Expanded and extruded thermoplastic foams made with methyl formate-based blowing agents

Description

Field of the Invention

[0001] The invention relates generally to foams using environmentally acceptable blowing agents, and to methods for their preparation. More particularly, the present invention relates to thermoplastic and polymeric foams made using methyl formate blowing agents, resulting in durable foams, and methods of making the same. Thermoplastic polymer foams are particularly suitable for use in a variety of packaging in the form of swollen foam spheres or extruded sheets and articles made therefrom, and for insulation applications such as insulation boards in building materials.

The basis of the invention

[0002] Thermoplastic foams made of alkenyl aromatic polymers (e.g. polystyrene) or polyolefin polymers (e.g. polyethylene or polypropylene) have a wide range of applications, particularly as insulating and sealing materials in packages. Alkenyl aromatic polymeric foams in the form of spheres or sheets having a thickness of less than about one-half inch are used in the manufacture of packaging materials such as containers (cups, bowls, grippers, picnic boxes) for hot and cold drinks or food, and for securing during transportation fragile or shock-sensitive articles through molten balls or sheet, which is thermoformed into molds to obtain the packing material of the desired shape. Foam balls are also used as a loose fill with padding material. Generally, insulating foams are manufactured to a thickness greater than about one-half inches. The insulation value of such foams is measured in terms of heat conduction resistance or as an - R value, per inch (or one centimeter) of foam thickness. Suitable insulating foams generally have an - R value of about 4.0 per inch (1.57 per cm) or greater. Packaging and insulation foam products with a thickness greater than about 0.5 inch (1.27 cm) are called planks or boards. It is desirable that the foams are dimensionally stable; this characteristic is even more desirable for planks or boards.

[0003] These and other polymer foams are generally made using a continuous process where a blowing agent-charged molten resin is extruded under pressure through a suitable die into a lower pressure atmosphere.

Alternatively, a batch or batch process may be used where small polymeric beads, also called particles or granules, are impregnated with a blowing agent and then rapidly heated to a temperature close to or above the glass transition temperature of the polymer-blowing agent system, or subjected to external stress to a temperature of transition to the glass transition of the polymer-blowing agent system.

[0004] Currently, common physical blowing agents in the production of thermoplastic polymer foams such as alkenyl aromatic polymers (e.g. polystyrene) or polyolefin polymers (e.g. polyethylene or polypropylene) are chlorinated hydrocarbons, hydrochlorofluorocarbons, or combinations thereof. Hydrocarbons with three or more carbon atoms, however, are volatile organic compounds (VOCs) which lead to smog formation. In addition, certain halogenated hydrocarbons are either compounds (VOCs) or high ozone depleting potential (ODP), or hazardous air pollutants (HAPs), and sometimes, may fall into one or more of these categories. Therefore, the use of hydrocarbons and halogenated hydrocarbons as blowing agents in the production of polymeric foams is not beneficial in terms of environmental protection and imposes many constraints on the manufacturing process, thus complicating and greatly increasing the cost of their production. For example, alkenyl aromatic polymeric packaging foams (spheres or sheets) of (e.g. polystyrene) are generally produced with VOCs such as butanes or pentanes, and insulation foams made with VOCs such as hydrocarbons and halogenated hydrocarbons, or non-VOC compounds such as 1-chloro-1,1-difluoroethane (HCFC-142b) alone or in combination with ethyl chloride which is classified both as VOC and HAP. Therefore, there is a need to minimize or eliminate the use of VOCs and / or HAPs as blowing agents in making polymeric foams.

[0005] Methyl formate is classified as a non-VOC compound (Federal Register, vol. 69, number 228, November 29, 2004), is a non-HAP compound, and has zero ODP. US Patent 6,753,357 describes the use of methyl formate to make durable, rigid isocyanate / polyol based polyurethane foams. It should be noted, however, that such polyurethane foams are thermosetting foams produced by a cross-linking and curing process. The dimensional stability or instability of the final polyurethane foam product, due to the properties of the blowing agent, is quite different from that of thermoplastic polymer foams.

There is therefore a need for blowing agents using methyl formate and environmentally friendly co-blowing agents, preferably non-VOC compounds and / or non-HAP co-blowing agents, as components of the blowing agent blend to make stable thermoplastics. foams, without gaining random product quality in terms of mechanical strength, crush strength or appearance, and insulating capacity, and enabling an economically efficient and universal production process. [0007] US Patent 3,914,191 describes the use of a methyl formate-trichloromonofluoromethane azeotrope as a blowing agent in the production of polystyrene foam.

Summary of the invention

[0008] It is an object of the present invention to provide a polymer foam structure. The object is achieved by the features defined in the independent claims. Further advantageous features are set out in the dependent claims.

[0009] According to one embodiment of the invention, the preferred blowing agent for making thermoplastic polymer foams is a blend comprising methyl formate and at least one co-blowing agent. The co-blowing agent is either a physical co-blowing agent (such as e.g. inorganic agent, hydrocarbon, halogenated hydrocarbon, ether, ester, acetal, alkanol, carbonate, amine, ketone, or any combination thereof), chemical co-blowing agent, or combinations thereof. In a preferred embodiment, the thermoplastic polymer foam is an alkenyl aromatic polymer foam. In a more preferred embodiment, the alkenyl aromatic polymer foam is expandable polystyrene foam (also called EPS), or extruded polystyrene foam (also called XPS), either of which may be used as packaging and insulation foam. According to a preferred embodiment, the blowing agent is a blend comprising any combination of methyl formate and one or more co-blowing agents. For packaging foams, the preferred co-blowing agent is a hydrocarbon, more preferably a hydrocarbon containing four or five carbon atoms, a halogenated hydrocarbon, an ether, an alkanol, a ketone, or any combination thereof. For insulation foams, especially boards or boards, the preferred co-blowing agent is hydrocarbon, more preferably, a hydrocarbon containing four or five carbon atoms, 1,1,1,2-tetrafluoroethane (HFC-134a), 1-chloro-1 , 1-Difluoroethane (HCFC-142b), or any combination thereof. Generally, the foam sheets or spheres are less than about 0.5 inches (1.27 cm) thick; insulating foam boards have a thickness of at least about 0.5 inches (1.27 cm), preferably about 0.5 inches to about 3 inches (1.27 cm to 7.62 cm), and an R-value of about 4 inches (1 , 57 cm) or larger. In accordance with another embodiment of the invention, the swellable polymer formulations are used to form a swellable thermoplastic polymer foam structure. The formulation comprises a thermoplastic polymer and a blowing agent including methyl formate and at least one co-blowing agent. The co-blowing agent is either a physical co-blowing agent (e.g., an inorganic, hydrocarbon, halogenated hydrocarbon, ether, ester, acetal, alkanome, carbonate, amine, ketone, water, or a combination thereof), a chemical co-blowing agent, or a combination thereof. . In a preferred embodiment of the invention, the thermoplastic polymer foam structure is an alkenyl aromatic polymer foam structure. In a more preferred embodiment of the invention, the alkenyl aromatic polymer foam is a expandable polystyrene (EPS) foam structure. In a preferred embodiment of the invention, the blowing agent is a blend comprising a combination of methyl formate and one or more co-blowing agents. For packaging foams, the preferred co-blowing agent is a hydrocarbon, more preferably a hydrocarbon having four or five carbon atoms, a halogenated hydrocarbon, an ether, an alkanol, a ketone, or combinations thereof, and for insulating foams, especially for boards or cartons, preferred the co-blowing agent is a hydrocarbon, more preferably a hydrocarbon having four or five carbon atoms, 1,1,1,2-tetrafluoroethane (HFC-134a), 1-chloro-1,1-difluoroethane (HCFC-142b), or any combination thereof. In a preferred embodiment of the invention, the formulation is in the form of swellable spheres.

According to another embodiment, the thermoplastic polymer foam structure is prepared by a process involving melting the thermoplastic polymer, mixing (e.g., dissolving, impregnating or trapping) an effective amount of a blowing agent, and forcing the pressurized mixture through a suitable nozzle into a reduced pressure zone to form foams. sheets or plates, or to a zone of lower temperature to form swellable spheres. In another aspect of the invention, the swellable spheres are made by dissolving an effective amount of a blowing agent into a thermoplastic polymer. In accordance with another aspect of the invention, the swellable spheres are made by synthesizing the polymer in the presence of the blowing agent until the blowing agent is dissolved, saturated, or absorbed into the polymer. The polymer may be in the form of pellets, preferably about 0.1 inch x 0.1 inch (0.254 cm x 0.254 cm), spheres or particles. The swellable foam structure is then obtained by rapidly heating the swellable spheres to a temperature near or above the glass transition temperature of the polymer blowing agent system to form foam spheres that can be used as such or further by compression molded into the desired shape and thickness. In accordance with another aspect of the invention, the intumescent foam structure is obtained by subjecting the spheres to an external compressive stress at the glass transition temperature of the polymer-blowing agent system. A preferred blowing agent to form a polymeric thermoplastic foam structure is a blend comprising methyl formate and at least one co-blowing agent. The co-blowing agent is either a physical co-blowing agent (such as e.g. inorganic agent, hydrocarbon, halogenated hydrocarbon, ether, ester, acetal, alkanol, carbonate, amine, ketone, water or any combination thereof), chemical co-blowing agent, or combinations thereof. In a preferred embodiment of the invention, the thermoplastic polymer foam structure is an alkenyl aromatic polymer foam structure. In a more preferred embodiment of the invention, the alkenyl aromatic polymer foam is either an expandable polystyrene (EPS) structure or an extruded polyester foam (XPS) structure, each used as a packaging or insulation foam. In a preferred embodiment of the invention, the blowing agent is a blend including any combination of methyl formate and at least one co-blowing agent. For packaging foams, the preferred co-blowing agent is a hydrocarbon, more preferably a four or five carbon hydrocarbon, a halogenated hydrocarbon, an ether, an alkanol, a ketone, or any combination thereof. For insulation foams, especially boards or boards, the preferred co-blowing agent is hydrocarbon, more preferably, a hydrocarbon containing four or five carbon atoms, 1,1,1,2-tetrafluoroethane (HFC-134a), 1-chloro-1 , 1-Difluoroethane (HCFC-142b), or any combination thereof. Generally, the foam sheets or spheres are less than about 0.5 inches (1.27 cm) thick; insulating foam boards have a thickness of at least about 0.5 inches (1.27 cm), preferably about 0.5 inches to about 3 inches (1.27 cm to 7.62 cm), and an R-value of about 4 inches (1.157 cm) or larger.

According to the method of the present invention, a thermoplastic polymer foam structure is prepared by a process involving melting the thermoplastic polymer, mixing (e.g., dissolving, impregnating, or trapping) an effective amount of the sensing agent, and extruding the pressurized mixture through a suitable nozzle into a reduced pressure zone to form sheets or boards. foam or into a zone of lower temperature to form swellable spheres. In another aspect of the invention, the swellable spheres are made by dissolving an effective amount of a blowing agent into a thermoplastic polymer. In accordance with another aspect of the invention, the swellable spheres are made by synthesizing the polymer in the presence of the blowing agent until the blowing agent is dissolved, saturated, or absorbed into the polymer. The polymer may be in the form of pellets, preferably about 0.1 inch x 0.1 inch (0.254 cm x 0.254 cm), spheres or particles. The swellable foam structure is then obtained by rapidly heating the swellable spheres to a temperature near or above the glass transition temperature of the polymer blowing agent system to form foam spheres that can be used as such or further compression molded into the desired shape and thickness. In accordance with another aspect of the invention, the intumescent foam structure is obtained by subjecting the spheres to an external compressive stress at the glass transition temperature of the polymer-blowing agent system. A preferred blowing agent for forming a polymeric thermoplastic foam structure is a blend comprising methyl formate and at least one co-blowing agent. The co-blowing agent is either a physical co-blowing agent (such as e.g. inorganic agent, hydrocarbon, halogenated hydrocarbon, ether, ester, acetal, alkanol, carbonate, amine, ketone, water or any combination thereof), chemical co-blowing agent, or combinations thereof. In a preferred embodiment of the invention, the thermoplastic polymer foam structure is an alkenyl aromatic polymer foam structure. In a more preferred embodiment of the invention, the alkenyl aromatic polymer foam structure is either an expandable polystyrene (EPS) structure or an extruded polyester foam (XPS) structure, each used as packaging or insulation foams. In a preferred embodiment of the invention, the blowing agent is a blend comprising any combination of methyl formate and at least one co-blowing agent. For packaging foams, the preferred co-blowing agent is a hydrocarbon, more preferably a four or five carbon hydrocarbon, a halogenated hydrocarbon, an ether, an alkanol, a ketone, or any combination thereof. For insulation foams, especially as boards or cardboard, the preferred co-agent is a hydrocarbon, more preferably a hydrocarbon containing four or five carbon atoms, 1,1,1,2-tetrafluoroethane (HFC-134a), 1-chloro-1, 1-Difluoroethane (HCFC-142b), or any combination thereof. Generally, the foam sheets or spheres are less than about 0.5 inches (1.27 cm) thick; insulating foam boards have a thickness of at least about 0.5 inches (1.27 cm), preferably about 0.5 inches to about 3 inches (1.27 cm to 7.62 cm), and an R-value of about 4 inches (1.157 cm) or larger. The structure of the polymer foam obtained by the process of the present invention is preferably substantially cell-closed and dimensionally stable. In a preferred embodiment of the invention, the alkenyl aromatic foam structure comprises a polystyrene polymer.

[0011] The formulations of the invention and the methods of the invention use blowing agents containing environmentally friendly, non-VOC and non-HAP compounds, and therefore offer significant advantages over current blowing agents.

[0012] Fig. 4 is a flowchart of the general sequence of operations necessary in the manufacture of an extruded foam board or plank in accordance with one embodiment of the invention.

[0013] While the invention is amenable to various modifications and alternative forms, specific embodiments of the invention show examples and describe details. However, it is understood that this is not intended to limit the invention to the specific embodiments disclosed herein, but on the contrary, the invention covers all modifications, equivalents, and alternatives falling within the scope and spirit of the invention as defined by the claims.

Description of illustrative solutions

[0014] The effectiveness of the blowing agent depends on its solubility in the polymer and its ability to swell the polymer-blowing agent solution when such solution is made thermodynamically unstable such that the solution is in the form of a die attached to an extruder (to form an extrudate) or when a polymer containing a blowing agent is rapidly heated. The extrudate swelling depends on the difference between the glass transition temperature of the thermoplastic polymer Tg and the boiling point of the blowing agent Tb. In general, the solubility of the blowing agent in the polymer depends on the difference between the temperatures Tg and Tb (Tg-Tb); the smaller the difference, the greater the solubility. Since volatility is inversely dependent on Tb, it should be understood that under the same temperature and pressure conditions, a more volatile blowing agent will have lower solubility compared to a less volatile blowing agent. In this way, by mixing the less volatile blowing agent with the more volatile blowing agent, a foaming formulation with optimal solubility and swelling properties can be obtained. Moreover, by mixing the presently used VOC or HAP blowing agent with a blowing agent of similar non-VOC and non-HAP volatility, emissions can be reduced without compromising the sacrificial solubility and swelling characteristics.

[0015] The foams and methods of the invention employ blowing agents to obtain a durable thermoplastic polymer foam. A preferred blowing agent used in the present invention includes methyl formate which is a non-VOC and non-HAP compound with a zero ODP value. Therefore, eliminating the HAP compound and minimizing the smog tendency from the production process and the foam obtained therein is not only safer and environmentally friendly, but also avoids the solubility and swelling characteristics. Moreover, by mixing the presently used VOC or HAP blowing agent with a blowing agent of similar non-VOC and non-HAP volatility, emissions can be reduced without compromising the sacrificial solubility and swelling characteristics.

[0016] The foams and methods of the invention employ blowing agents to obtain a durable thermoplastic polymer foam. A preferred blowing agent used in the present invention includes methyl formate which is a non-VOC and non-HAP compound with a zero ODP value. Therefore, eliminating the HAP compound and minimizing the smog tendency of the manufacturing process and the resulting foam therefrom is not only safer and environmentally friendly, but also avoids many of the disadvantages of currently used blowing agent compositions and processes. Therefore, methyl formate as such or in combination with one or more suitable blowing agents having similar environmental properties, but also additionally lower thermal conductivity, can help shift the harmful effects on the environment (ODP, HAP, VOC) associated with current measures. blowing agents.

[0017] The resins that can be expanded in accordance with the invention include melt-processed thermoplastic polymers such as alkenyl aromatic polymers, polyolefins, polycarbonates, polyacrylates, and others. The term thermoplastic polymer includes both amorphous and semi-crystalline polymers. Examples of amorphous thermoplastic polymers include, but are not limited to, polystyrene, polycarbonate, poly (methyl methacrylate), and poly (phenylene oxide). Examples of semi-crystalline thermoplastic polymers include, but are not limited to, polyethylene, polypropylene, syndiotactic polystyrene, polyethylene terephthalate.

[0018] An embodiment of the invention relates to alkenyl aromatic polymers. The term "alkenyl aromatic polymer" as used herein includes polymers of aromatic hydrocarbon molecules that contain an aryl group linked to an olefin only through double bonds in a linear structure, such as styrene, or styrene homologues such as α-methylstyrene, o-, m-, and p -methylstyrene, α-ethylstyrene, o-, m-, petylstyrene, 2,4-dimethylstyrene, α-vinylxylene, and vinyltoluene. The alkenyl aromatic polymers also include styrene homopolymers or styrene homologues (commonly referred to as polystyrene), styrene copolymers, and rubber curable polystyrene (commonly referred to as high impact polystyrene, HIPS). As for the styrene copolymer, the comonomer may generally be any other ethylenically unsaturated substance such as conjugated 1,3-dienes, e.g. butadiene, isoprene, alpha-beta-unsaturated monocarboxylic acids and their derivatives, e.g. acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the corresponding methacrylic acid esters, acrylamide, methacrylamide, acrylonitrile and methacrylonitrile. If desired, blends of a styrene polymer with other polymers may be used, e.g., blends of a styrene polymer with poly (phenylene oxide). Preferably, the copolymers contain a predominant proportion of styrene, e.g., greater than about 50% by weight styrene, and more preferably greater than 75% styrene.

[0019] The blowing agent is a blend containing less than 100 mole% methyl formate, including at least one co-blowing agent. It is contemplated that more than one co-blowing agent may be used in the blowing agent blend. The co-blowing agent can be physical, chemical, or combinations thereof. The composition of the blowing agent blend depends on the foamed structure being produced. In one embodiment, when the foamed structure is a sheet or a swellable ball, the blowing agent blend comprises from about 1 mole% to about 100 mole% methyl formate. In another embodiment, however, when the foamed structure is a swellable ball, sheet, plate, or board, the blowing agent blend includes from about 1 mole% to about 99 mole% methyl formate, and at least one co-blowing agent.

[0020] The co-blowing agent can be physical, chemical or a combination thereof. The co-blowing agent generally expands rapidly compared to pure methyl formate blowing agent. The co-blowing agent can be an organic compound or an inorganic compound. Preferably, the co-blowing agent is a non-VOC compound. Still preferably, the co-blowing agent is a non-HAP compound. More preferably, the co-blowing agent is a non-VOC and non-HAP compound. Some non-limiting examples of physical co-blowing agents include, but are not limited to, inorganic agents, organic agents (e.g., hydrocarbons, halogenated hydrocarbons, ethers, esters, acetals, alkanols, carbonates, amines, and ketones), or any combination thereof.

[0021] Some suitable inorganic physical blowing agents include, but are not limited to, carbon dioxide, water, air, nitrogen, argon, xenon, sulfur hexafluoride, nitrous oxide, ammonia, silicon tetrafluoride, nitrogen trifluoride, boron trifluoride, and boron trichloride, but not limited to their combination. In one currently preferred embodiment, the inorganic agent is an inorganic gas such as carbon dioxide, nitrogen, argon, and air. The currently preferred inorganic gas is carbon dioxide. In another currently preferred embodiment, the inorganic agent is water.

Some examples of organic physical co-blowing agents that can be used in the invention include, but are not limited to, hydrocarbons, halogenated hydrocarbons, polar group fluids such as ethers, esters, acetals, carbonates, alkanols, amines, and ketones and combinations thereof. Examples of hydrocarbons include, but are not limited to, methane, ethane, propane, cyclopropane, n- or iso-butane, cyclobutane, neopentane, and isopentane, or any combination thereof. Examples of halogenated hydrocarbons include, but are not limited to, methyl fluoride, difluoromethane (HFC32), trifluoromethane (HFC-23), perfluoromethane, chlorodifluoromethane (HCFC-22), methylene chloride, ethyl chloride, ethyl fluoride, 1,2-difluoroethane ( HFC-152), 1,1-difluoroethane (HFC152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), pentafluoroethane (HFC-125), perfluoroethane , 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124), difluoropropane, 1,1,1-trifluoropropane, 1,1 , 1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,2,3,3-hexafluoropropane (HFC-236ea), 1,1,1,2,3,3,3 heptafluoropropane (HFC-227ea), perfluoropropane, 2,2,4,4,4-pentafluorobutane (HFC

20365mfc), perfluorobutane, perfluorocyclobutane, and vinyl fluoride, or any combination thereof. Polar group fluids include, but are not limited to, ethers such as dimethyl ether, methyl vinyl ether, ethyl methyl ether, fluorodimethyl ether, fluorodiethyl ether, and perfluorotetrahydrofuran; amines such as dimethylamine, trimethylamine, and ethylamine; ketones such as acetone and perfluoroacetone; esters such as ethyl formate and methyl acetate; acetals such as methylal; carbonates such as dimethyl carbonate, alkanols such as ethanol, or any combination thereof. Presently preferred organic co-agents are hydrocarbons containing four or five carbon atoms, HCFC-142b, and HFC-134a.

[0023] Chemical co-blowing agents are compounds that undergo a chemical reaction, e.g. decomposition, to form an inorganic gas such as CO2, N2. or CO. Non-limiting examples of suitable chemical co-blowing agents include azodicarbonamide, azodiisobutyronitrile, benzenesulfonohydrazide, 4,4'-oxybis (benzenesulfonylhydrazide), p-toluenesulfonylsemicarbazide, barium azodicarboxylate, N, N'-dimethyl-N-triazide, Nereydrazamiditrile compounds , N-nitrosides, carbonates and sulfonyl hydrazides. There are also various acid / bicarbonate mixtures that decompose into gases on heating. For example, mixtures of citric acid and sodium bicarbonate sold under the name HYDROCEROL® may be used as chemical co-blowing agents.

The total amount of blowing agent used in the polymer formulation used to form the thermoplastic polymer foamed structure depends on the conditions such as the temperature and pressure at which the blowing agent is dissolved in the polymer, the chemical and thermoplastic characteristics of the blowing agent used, and the desired density and properties. accompanying, such as insulation value, weight / strength ratio, and the crush strength of the foam product. Polymer article or foamed article is defined herein as including blowing agent (s), polymer resin (s), and any additives. For a foam having a density of from about 1 to about 15 lb / ft3 (0.016 to 0.240 g / cm3), the extrudate typically contains from about 18 to about 1% by weight of the blowing agent.

[0025] The blowing agent used in the present invention comprises 100% methyl formate, or the blowing agent may be a blend and contain 99 mole% or less of methyl formate in combination with one or more co-blowing agents which may be a physical co-blowing agent, a chemical co-inflator or a combination thereof. The blowing agent blend generally comprises from 1 mole% to about 99 mole% methyl formate, such as from about 5 mole% to about 75 or 80 mole% methyl formate, or from about 20 mole% to about 80 mole% methyl formate. More typically, the blowing agent blend comprises from about 20 or 25 mole% to about 60 mole% methyl formate. More specifically, the blowing agent blend preferably comprises from about 20 or 25 mole% to about 50 mole% methyl formate.

[0026] If used, the blowing agent blend generally comprises at least about 20 or 25 mole% of co-blowing agent (s). The blowing agent blend more typically comprises from about 80 or 75 mole% to about 40 mole% co-blowing agent (s). More specifically, the blowing agent blend preferably comprises from about 80 or 75% to about 50% by mole of co-blowing agent (s).

[0027] For example, according to a preferred embodiment, the blowing agent blend comprises from about 30 mole% to about 50 mole% methyl formate, and from about 70 mole% to about 50 mole% co-blowing agent.

[0028] According to the invention, a nucleating agent or a combination of such agents may be used in the polymeric foam formulation because of advantages such as their ability to regulate cell formation, morphology, and performance characteristics of the foamed article. The amount of nucleating agent used depends on the desired cell size, the selected blowing agent blend and the desired foam density, and performance characteristics of the foamed article. The nucleating agent is generally added in an amount from about 0.02 to about 2.0% by weight of the polymer resin composition.

[0029] Some contemplated nucleating agents include inorganic substances (as small particles, preferably with high ratio (> 20) and a particle size in the micrometer to sub-micrometer range), such as clay, talc, silica, and diatomaceous earth. For example, talc can be used in an amount from about 0.25 to about 2.0% by weight of the polymer composition. Other examples of nucleating agents include organic nucleating agents that decompose or react under heating in the extruder, releasing gases such as carbon dioxide and / or nitrogen. One example is the combination of an alkali metal salt of a polycarboxylic acid with a carbonate or bicarbonate. Some examples of the alkali metal salt of a polycarboxylic acid include, but are not limited to, 2,3-dihydroxybutanedioic acid monosodium salt (commonly referred to as sodium bitartrate), butanedioic acid monopotassium salt (commonly referred to as potassium hydrogen succinate), trisodium and tripotassium 2-hydroxy acid salts1,2 , 3-propanetricarboxylic acid (commonly referred to as sodium and potassium citrate, respectively), and ethanedioic acid disodium salt (commonly referred to as sodium oxalate) or a polycarboxylic acid such as 2-hydroxy-1,2,3-propane tricarboxylic acid. Some examples of a carbonate or bicarbonate include, but are not limited to, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and calcium carbonate.

[0030] It is contemplated that mixtures of different nucleating agents may be added in the present invention. Some of the more desirable nucleating agents include talc, crystalline silica, and a stoichiometric mixture of citric acid and sodium bicarbonate (the stoichiometric mixture has a concentration of 1 to 100 percent when the carrier is a suitable polymer). The talc can be added on a carrier or in the form of a powder.

[0031] If desired, flame retardants may also be used in the present invention. Examples of flame retardants, but not limited to, include bromine compounds, chloro paraffin and other chlorine compounds, antimony trioxide, and aluminum trihydrate.

[0032] If desired, fillers, dyes, light and heat stabilizers, antioxidants, acid scavengers, stability control agents, processing aids, extrusion aids, and foaming additives can be used in making the foam.

[0033] In accordance with the invention, any of a variety of suitable extrusion system and methods known in the art may be used to dissolve the blowing agent in polymers. One example of a suitable system and methods includes, for example, a typical tandem of two extruders, each extruder having a single screw. Alternatively, a tandem of two extruders may be used to extrude the foam product of the invention, wherein the first extruder has a twin screw and the second extruder has a single screw. According to the invention, it is also possible to use a single extruder with adequate cooling.

[0034] According to one method of the invention, thermoplastic polymer (e.g. polystyrene) pellets are mixed with a nucleating agent such as talc. These materials are continuously introduced into the extruder basket. The raw material mixture is conveyed forward by a screw in an extruder barrel, where the mixture is mixed, compressed, heated and molten. Conversion to molten form occurs prior to reaching the injection zone where the blowing agent is added. The blowing agent blend of the invention can be injected into the polymer composition at the point where the polymer is in a molten state (i.e., outside the feed zone). Each of the components of the blowing agent blend may be individually injected, either sequentially or simultaneously and in any order, into the molten polymer. Alternatively, the components of the blowing agent blend may be pre-mixed and the mixture injected into the polymer composition. If a tandem of two extruders is used, the agent (s) may be injected either into the first or second extruder, or some components of the composition may be injected into the first extruder and the remaining ingredients into the second extruder.

[0035] Following injection of the blowing agent, the various components in the extruder are continuously mixed under pressure to obtain a homogeneous solution of the polymer and the blowing agent. The molten solution is then transported to a cooling zone where additional mixing takes place. After cooling, the mixture is extruded into a storage zone maintained at a temperature and pressure that protects or inhibits foaming of the mixture. The containment area has (a) the die casting mold outlet has an opening facing a lower pressure zone, such as atmospheric pressure, (b) a device for closing the opening without disturbing the foaming mixture inside the containment zone, and (c) an opening device that allows ejection of the foaming mixture from the storage area. An example of a storage zone is described in US 4,323,528. Whether or not a holding zone is used, the solution is then forced through the die-casting mold into a lower pressure zone, such as atmospheric pressure. After exiting, the extrudate remains as a foam or is immediately subjected to a temperature reduction (e.g. by contacting the extrudate with a heat exchange fluid such as water), and the solidified extrudate is chopped into small spheres that can be expanded into a foam at a later time if desired.

According to one embodiment, for extruding a foam product (e.g., sheet) according to the invention, it can be used with alkenyl aromatic polymers such as polystyrene, in tandem of two extruders as shown in Fig. 1, or to produce swellable spheres as shown in Fig. 1. Fig. 2. The polymer resin pellets are mixed with one or more additives (e.g. a nucleating agent and / or a stability adjusting agent), if desired, to form a feed mixture which is continuously introduced into basket 11 of the first extruder 13. The feed mixture is forwarded by a helical screw inside the cylinder of the first extruder, wherein the feed mixture is mixed is compressed, heated and melted before the blowing agent enters the injection zone. The blowing agent blend is added at point 15. Thus, the inventive blowing agent blend is injected into the polymer / additive blend (raw material mixture) at a point outside the feed zone where the polymer is in a molten state. If desired, the blowing agent blend can be injected at other locations outside the feed zone, including the second extruder.

After injection of the blowing agent, the ingredients are continuously mixed in the first extruder 13. The outlet pressure from the first extruder 13 in accordance with the exemplary embodiment is generally in the range of about 1500 to about 4000 psi (10.3 MPa to 27.6 MPa). MPa). The temperature of the first extruder 13 of the exemplary embodiment is generally in the range of from about 390 to about 475 ° F (199 to 246 ° C). The mixture is then passed, under sufficient pressure that the blowing agent blend remains in solution, through the hollow linkage section 17 to the cooled tandem of the second extruder 19. The molten mixture is passed along the length of a cooled second extruder under low shear where additional cooling occurs and mixing. The pressure at the outlet from the second extruder 19 of the exemplary embodiment is generally in the range of about 1000 to about 2500 psi (6.9 MPa to 17.2 MPa). The temperature of extrudate from the second extruder 19, in accordance with the exemplary embodiment, is generally in the range of from about 240 to about 320 ° F (115 to 160 ° C). In general, the temperature of the first extruder should be sufficient to melt the polymer and any additives and to promote efficient mixing. The temperature and pressure in the second extruder should be sufficient to maintain the homogeneous solution of the ingredients in the molten state. It is understood that the temperatures, pressures, and other conditions described may vary depending upon the properties of the thermoplastic polymer used in the process. The specific conditions for use are apparent to the person skilled in the art.

As can be seen from Fig. 1, to produce a foam sheet, the molten product is pressed through the annular die 21 in the low pressure zone into a mold of an elongated cylinder or tube 23, and a foamed polymer is drawn through the cylindrical surface of the cooling and finishing drum 25. and slit to form a sheet product 27 which is then fed to one or more reels 29.

[0039] Alternatively, as shown in Fig. 2, to form swellable polymer spheres, the molten product is forced through a strip or bar die 28 into a low temperature zone 30 containing a warm heat exchange fluid 32 such as water. In this way, the molten solution solidifies into strands, typically 0.1 inch (0.254 cm) in diameter, without undergoing any expansion or foaming. The drawn strands then pass through the breaker 34 or other cutting device, and are cut into pellets (typically 0.1 inch x 0.1 inch (0.254 cm x 0.254 cm) to form so-called swelling spheres 36.

[0040] In another embodiment of the invention, instead of using the continuous fusing process as described in Fig. 2, swellable spheres may be made without a blowing agent by exposing the solid polymer granules to the blowing agent in a pressurized container for a period of time to saturation limit. This saturation step can be carried out at a slightly elevated temperature to accelerate the impregnation with the blowing agent to form solid lumps. However, the temperature should not be too high to allow the saturated lumps to stick together. In yet another method, impregnation with the blowing agent may be accomplished by carrying out polymer synthesis in the presence of the blowing agent until the blowing agent is dissolved, saturated, or entrapped in the polymer.

[0041] The swellable spheres produced by any method are then expanded as shown in Fig. 3, in Step 2, by rapidly heating the spheres to a temperature close to or above the Tg temperature of the polymer-blowing agent system, e.g. by contacting the saturated spheres with water vapor. Saturated granules can also be foamed below the Tg temperature by applying mechanical pressure (compressive stress) to induce nucleation and cell growth, as described in US 6,080,798. Regarding the methods used, the spheres rapidly expand into foam spheres (Stage 2), which age under ambient conditions (Stage 3), for example by cooling the spheres to ambient temperature, allowing air to diffuse into the foamed spheres until the dimensions stabilize. These balls can be used as such, for example as a loose filler for packages as shown in Step 4. Alternatively, the foamed and aged spheres can be melted together in a heated mold as shown in Step 5 to form products of any variety of shapes such as cups, plates, embossed packages, containers, slabs or boards. Further reduction in density occurs during the air forming operation, and the remainder of the blowing agent for swelling the beads provides a further expansion.

[0042] In yet another configuration, as shown in Fig. 4, the foamable formulation is pressed through a die of a different configuration to that of a flat die 20 and allows it to expand into a plate or plank 24. The expanded extruded product 22 is removed via rollers 26 , and may be further directed to the shape modeling device prior to being formed into a board or plank 24.

[0043] Depending on the materials and process used, the resulting foamed product may be in the form of spheres, sheets, boards or boards. The foamed spheres can be further processed into a sheet, plate or plank, or into articles of various shapes, sizes and thicknesses. If the article produced is in the form of a sheet, the thickness of the sheet will generally be equal to or greater than 0.5 inch (1.27 cm), preferably in the range of between 0.5 inch and 3 inch (1.27 cm and 7.62 cm). ).

[0044] For making thermoplastic polymer foam sheets, the use of an annular die is preferred. Articles produced with the annular die are generally less than about 0.5 cm (1.27 cm) thick, preferably from about 0.125 to about 0.438 inch (0.317 to 1.11 cm) thick. For the manufacture of thermoplastic polymer foam boards, e.g., insulation boards, it is preferred to use a flat die. Articles produced with a flat die are generally at least about 0.5 cm (1.27 cm) thick. For example, in a preferred embodiment of the invention, for insulating materials, the thickness is from about 0.5 to about 3 inches (1.27 to 7.62 cm). Such a board is of particular use as an insulating material, e.g. as an insulating board or board. With respect to the type of die used or the foam to be formed, the extruded foam may be subjected to further expansion or density reduction by the application of heating or vacuum.

[0045] The foam balls, sheets and boards or planks may be used as such, cut into appropriate shapes, then shaped by the application of heat or pressure, or otherwise, or formed into other shaped articles of the required size and shape known from the state of the art. techniques.

Depending on the materials and process used, the resulting foamed product generally has a density of from about 1 to about 15 lb / ft2 (0.016 to 0.240 g / cm2, a further reduction in density achieved by a subsequent second swelling after application of heat and / or Typically, the density of the foamed spheres is less than 1.0 lb / ft3 (0.016 to 0.240 g / cm3). The foam sheets generally have a density of about 2 to about 9 lb / ft. (0.016 to 0.240 g / ft3 while foam sheets used for insulation purposes generally have a density of about 1.5 to about 3.5 lb / ft. (0.016 to 0.240 g / cm3) Further, and in accordance with one preferred embodiment of the invention, the resultant foamed article has an essentially closed-cell structure and is defined herein as a foam having greater than about 85% closed cells, and more typically greater than about 95% closed cells. Alternatively, and in accordance with another aspect of the invention, the resultant foamed article may be made up of 15% or more open cells, e.g. 20%, 25%, 30% or more open cells. In addition, the resulting foam structure can be inspected to contain at least about 25, 30, 35, 40, 45, or 50 cells per inch (approximately 10, 12, 14, 16, 18, or 20 cells per cm) for expanded beads. and sheets, and at least about 50, 55, 65, 75, 85, 95, or 100 cells per inch (approximately 20, 22, 24, 25.5, 30, 33, or 40 cells per cm) for embossed boards.

[0047] The term "R value" refers to a unit of thermal resistance used to compare the insulating values ​​of various materials known in the art. Generally, the higher the R-value, the better insulation resisting heat transfer. Many factors can influence the R-value of the insulation, including the type of blowing agent used and the age of the foam. R values ​​are generally expressed in terms of standard material thickness units. For example, the R value for foams can be measured for every inch of the thickness of the foam. Suitable insulating foams, such as those of the present invention, preferably have an R value of about 4.0 per inch (1.57 per cm) or greater. For example, and in a preferred embodiment, the insulating foams of the present invention have an R value per inch of greater than about 5 (1.96 per cm). The R-value of the foams of the invention is determined by conventional methods, for example by ASTM C518.

[0048] The foam according to the invention can be used as insulation or as building materials, in various containers and packaging systems, or as protective or flexible packaging. Generally speaking, foam sheets are used in flexible as well as rigid packages, while foam boards are used in protective packages; extruded foam boards having a thickness greater than about 0.5 inches are used for insulation purposes, for example as building materials; swollen spheres are used as fillers in packages, or are formed into sheets or planks, or slabs, or profiled articles for flexible, protective, rigid, and insulating applications. In addition to foam sheets, planks and boards, the present invention can be embodied in other shapes such as rods, pipes, or other profiles.

[0049] Other uses for the foams of the invention, as well as corresponding processes, apparatus, equipment, devices and systems for making them, are described in US Pat. US Of North America and published applications 6,136,875, 5,149,473, 6,476,080, 6,599,946, 6,696,504, US 2004/0132844 and US 2004/0006149.

Dimensional stability is generally expressed in terms of% thickness change, which is 100 x (aged thickness - starting thickness) / starting thickness, the initial thickness being measured within 15 minutes after extrusion. The resulting foam of the invention has the desired "dimensional stability" except that the thickness of the foam after 7 days aging does not change by more than about 15%, preferably not more than 10%, and more preferably not more than 5% of the fresh extruded thickness. foam. Preferably, the foams of the invention exhibit a dimensional change of less than about 4%, more preferably less than about 1% in each direction.

[0051] The following examples are presented in order to more fully illustrate some embodiments of the invention. These examples, however, in no way limit the scope of the invention. One skilled in the art will readily make many variations and modifications to the general principles of the invention disclosed herein without departing from the scope of the invention.

Examples

Example A

[0052] In the following table 1 pr shows the test results of various blowing agents. Specifically, foam sheets of various alkenyl aromatic polymers were made using the comparative blowing agents and blowing agents of the invention in accordance with the extrusion process generally described herein. It should be noted that in the various examples listed in Table 1, the same devices were used and operated in exactly the same manner; the only variable was the blowing agent. All the inventive blowing agents contained methyl formate; and the comparative blowing agent (s) did not contain methyl formate.

[0053] Each of the alkenyl aromatic polymer foams was made in a tandem extrusion line using a 2.5 inch and 3.5 inch (6.35 and 8.9 cm) single screw extruder and a blowing agent was injected through a single orifice in the first extruder. General purpose polystyrene with high heat of combustion, density 1.05 g / cm 3 and a melt flow rate of 1.6 g / 10 min at 200 ° C under a load of 5 kg was used as the polymer resin. In addition to the blowing agents and polystyrene resin, talc was added up to 2% by weight of the total foaming composition, including the blowing agent (s), polymer resin (s) and additives. An annular die and an expansion extruder were used which were directed directly into the shaping system to form the foam sheets. An example of suitable equipment for making alkenyl aromatic polymer foam sheets is described in US Patent 6,136,875.

Table 1

Table 1

<td rowspan="2">% Thickness Change ^</td><td>7 days</td><td> 11,1</td><td> 12,9</td><td> 5,6</td><td> -3,9</td><td> 21,7</td><td> 4,7</td><td> 1 7,6</td><td> 9,0</td><td> 15,1</td><td> 9,5</td>

<td>1 hour</td><td> 0,8</td><td>ABOUT\</td><td> -0,3</td><td> -10,6</td><td> -0,3</td><td>n-</td><td>about</td><td> -6,6___</td><td> 0,1</td><td> 0,6</td>

<td>Cell dimension ^</td><td>JAM</td><td> 200</td><td> 196</td><td> 187</td><td> 209</td><td> 170</td><td> 234</td><td> 179</td><td> 210</td><td> 224</td><td> 254</td>

<td>Open cells</td><td></td><td> 8*1</td><td> 1,0</td><td> 2,2</td><td> 5,6</td><td> 23,5</td><td> 2,2</td><td> 1,8</td><td> 3,0</td><td></td><td>UD co</td>

<td>Density</td><td>(gtuo / S) _£wqi</td><td> 5,5 (0,088)</td><td> 4,7 (0,0752)</td><td> 8,1 (0,13)</td><td> 5,6 (0,09)</td><td> 8,6 (0,138)</td><td> 5,8 (0,093)</td><td> 4,1(0,066)</td><td> 4,4 (0,07)</td><td> 3,6 (0,0576)</td><td> 3,5 (0,056)</td>

<td>Talc</td><td>wt.% l</td><td> 1,8</td><td> 1,0</td><td>6'T</td><td>θ '</td><td> 0,7</td><td> 0,7</td><td> 0,6</td><td>θ '</td><td> 0,3</td><td> 0,3</td>

<td rowspan="8">Blowing agent (s) used (wt%)</td><td> 0¾</td><td></td><td></td><td></td><td></td><td> 0,50</td><td></td><td></td><td></td><td></td><td></td>

<td>What S.</td><td></td><td></td><td> 4,30</td><td> 3,32</td><td> 1,95</td><td> 3,52</td><td> 2,40</td><td> 1,97</td><td>Ul</td><td> 0,34</td>

<td>CN Fr.</td><td></td><td>θ '</td><td></td><td> 0,76</td><td> 0,50</td><td></td><td></td><td> 0,55</td><td> 0,37</td><td>(O θ '</td>

<td>Isopentane</td><td> 5,20</td><td> 3,96</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>n-butane</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>Isobutane</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>Propane</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td> 1,22</td><td> 2,01</td><td> 2,67</td>

<td>Ethane</td><td></td><td></td><td></td><td></td><td></td><td> 0,56</td><td> 1,00</td><td></td><td></td><td></td>

<td>A sample</td><td>Pp / Pww ^</td><td>Ppl</td><td>Pp2</td><td>Pwwl</td><td>Pww 2</td><td>Pww3</td><td>Pww4</td><td>Www 5</td><td>Pww6</td><td>Www 7</td><td>Www 8</td>

<td>6'ΙΤ</td><td> 13,2</td><td> 13,7</td><td> 22,1</td><td> 10,7</td><td> 18,4</td><td rowspan="15">1. wt.% = (weight of ingredient) / (total weight of foaming composition including blowing agent (s), polymer resin (s) and additives combined) 2. Pp - comparative example; Pww - an example according to the invention 3. MF - methyl formate 4. Number of cells per inch of extruded foam ranging from 210 to 420 (82 to 165 cells per cm). Cell size (expressed as diameter) determined by scanning with an electron microscope an image of an embossed sheet that has been aged for at least 24 hours and then expanded in the z direction (along the thickness direction) at a 240 ° F (115.5 ° C) oil bath for 2 minutes while limiting mechanically in x and y directions; the number of cells per inch in these blown samples ranged from 110 to 210 (43.3 up to 82.5 per cm).</td>

<td> 0,1</td><td> -0,3</td><td> 0,5</td><td> -3,5</td><td>tr? 1</td><td>L'L ~</td>

<td> 194</td><td> ___197</td><td> 166</td><td> 183</td><td> 180</td><td> 163</td>

<td>1.8 ______ I</td><td>⁶'·</td><td> 0,9</td><td>CM</td><td> 3,0</td><td> 1,7</td>

<td> 4,1 (0,066)</td><td> 4,0 (0,064)</td><td> 3,9 (0,062)</td><td>OO σ \ ξ</td><td> 5,3 (0,085)</td><td> 4,7 (0,075)</td>

<td> 1,0</td><td> 1,0</td><td> 1,0</td><td> 1,0</td><td>O'I</td><td> 1,4 \</td>

<td></td><td></td><td></td><td></td><td></td><td></td>

<td>CM</td><td> 0,74</td><td> 1,17</td><td> 1,82</td><td> 1,00</td><td> 1,20</td>

<td> 0,35</td><td> 0,35</td><td> 0,31</td><td>cn θ '</td><td> 0,78</td><td> 0,35</td>

<td></td><td></td><td></td><td></td><td> 2,79</td><td></td>

<td></td><td></td><td></td><td></td><td></td><td> 2,63</td>

<td> 3,57</td><td> 3,04</td><td> 2,65</td><td>about cm</td><td></td><td></td>

<td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td></td><td></td><td></td>

<td>Www 9</td><td>Www 10</td><td>Www 11</td><td>Pww 12</td><td>Pww 13</td><td>Inv 14</td>

All of the foams shown in Table 1 above were dimensionally stable, except for Inventive Example 2, they increase in thickness after extrusion. This unidirectional variation is different from the commonly used definition of dimensional stability and the foam may either shrink or expand over time. The compositions described herein result in permanent foam structures produced by an environmentally friendly and cost effective process. Moreover, various foams with suitable and desired properties can be formed in accordance with the invention. For example, composition 3 of the invention has the highest percentage of open cells, and thus is preferred as the flammable properties of the foam are reduced with increasing percentage of open cells due to the significant reduction in the inflammatory component (s) of the blowing agent blend. According to another example, compositions 2 to 5 of the invention contain ingredients with minimal and negligible impact on air quality. Comparative Example 2 shows a typical formulation widely used in the manufacture of polystyrene foam sheet or expanded beads. Other variants of this formulation, also widely used, occur when isopentane is replaced with n-pentane, or with isobutane or n-butane. Examples 6 to 14 of the invention show how a foam sheet (and by broadening the term, swollen spheres) with similar properties can be made using a formulation in which the use of a VOC-based blowing agent has been significantly reduced. A widely used blowing agent for producing swollen spheres is pentane, which has a boiling point of 36 ° C, a heat of vaporization of 25.8 kJ / mol at the boiling point; the corresponding value for methyl formate is 32 ° C, respectively, and the heat of vaporization is 27.9 kJ / mol. The combination of an agent with a lower boiling point and a higher heat of vaporization of methyl formate corresponds to a higher volatility and therefore has a better swelling effect than pentane. Consequently, the partial or complete replacement of pentane by methyl formate leads to a significant reduction in VOC emissions during the formation of swollen spheres (Fig. 3, Step 2), and the forming operations (Fig. 3, Step 5), and after operations following manufacturing such as like storing foam or product.

[0053] Moreover, it should be noted that the total number of moles of the blowing agent in all the formulations indicated in Table 1 is the same (about 0.07 moles per 100 g of total material processed). Obtaining different densities of foams thus simply reflects the effective volatility of the blowing agent blend. It will be appreciated by those skilled in the art that lower density foams can be obtained by varying the composition of the blowing agent blend and enriching it with more volatile component (s), and that the density can be further reduced by increasing the moles of the blowing agent blend. Each of the compositions according to the invention indicated in table 1 improves the quality of the foam, which is durable and easy to produce and handle.

Example B

[0054] Table 2 below shows the test results of various blowing agents used in forming insulating foam boards or boards. Specifically, various alkenyl aromatic polymeric foam sheets useful for insulation purposes have been made from the blowing agent blends of the invention according to the extrusion process generally described herein. It should be noted that in the various examples listed in Table 2, the same devices were used and operated in exactly the same manner; the only variable was the blend of the blowing agent and the corresponding percentage of polystyrene polymer. All the blowing agent blends of the present invention contained methyl formate in combination with the co-blowing agent HFC-134a.

Each of the alkenyl aromatic polymer foams was made in a tandem extrusion line using 1.0 inch and 1.5 inch (2.54 and 3.81 cm) single screw extruder equipped with three openings in the first extruder for injecting pressurized fluid. . The effluent rate was 10 lb / h (4.54 kg / h). The polymer resin used was general purpose polystyrene with a high heat of combustion value and a melt flow rate of 1.6 (PSI), general purpose polystyrene with a high heat of combustion value and a melt flow rate 11 (PS2), and polystyrene advertised by the Applicant in the insulation log process, with a melt flow rate of 11.5 (PS3). Talc was added up to 2.5% virgin polystyrene (PSI + PS2). A flat die was used and the swellable product was directed into the mold shaping system to form foam boards with a nominal diameter of 5.0 inch (width) x 0.5 inch (thin) (12.7 cm (width) χ 1.27 cm (thin). The shaping device used may be configured to form a preferred normal direction of the cells as shown in Table 2.

[0056] Table 2 shows various examples of formulations used to make insulating foam boards from an extrudate containing polyester, talc, methyl formate, HFC-134a and optionally CO2 according to the present invention. In addition, Table 2 shows the melting points of each foam product prior to extrusion. Table 2 also shows the density, R-value, cell size of the respective planks or slabs made up of the various exemplary formulations.

Table 2

<td>Example</td><td>Compare 3</td><td>Out 2</td><td>He fired 3</td><td>Out 4</td><td>He released 5</td><td>Out 6</td><td>Out 7</td><td>He released 8</td>

<td>PSI (wt% y</td><td> 99,00</td><td> 66,00</td><td> 66,00</td><td> 66,00</td><td> 66,00</td><td> 66,00</td><td> 66,00</td><td> 50,00</td>

<td>PS2 (wt%)^J.</td><td> 0,00</td><td> 32,35</td><td> 0,00</td><td> 0,00</td><td> 0,00</td><td> 0,00</td><td> 0,00</td><td> 0,00</td>

<td>PS3 (wt%)^!</td><td> 0,00</td><td> 0,00</td><td> 32,35</td><td> 32,35</td><td> 32,68</td><td> 32,68</td><td> 32,68</td><td> 50,00</td>

<td>Talc (wt%) '</td><td> 1,00</td><td> 1,65</td><td> 1,65</td><td> 1,65</td><td> 1,32</td><td> 1,32</td><td> 1,32</td><td> 0,00</td>

<td>Formate Methyl (pph)²</td><td> 2,42</td><td> 2,61</td><td> 3,42</td><td> 4,72</td><td> 4,07</td><td> 4,24</td><td> 3,95</td><td> 3,73</td>

<td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>HFC-134a (pph)²</td><td> 2,01</td><td> 2,73</td><td> 5,17</td><td> 4,72</td><td> 3,99</td><td> 5,50</td><td> 6,17</td><td> 5,83</td>

<td>What₂(pph)²</td><td> 0,00</td><td> 0,00</td><td> 0,00</td><td> 0,00</td><td> 0,36</td><td> 0,00</td><td> 0,00</td><td> 0,00</td>

<td>Temp, top (° C)³</td><td> 149</td><td> 141</td><td> 131</td><td> 121</td><td> 122</td><td> 121</td><td> 120</td><td> 121</td>

<td>Fresh density (pcf) [g / cm³]^4/5</td><td> 3,88 [0,062]</td><td> 3,15 [0,050]</td><td> 2,70 [0,043]</td><td> 2,52 [0,040]</td><td> 2,67 [0,043]</td><td> 2,67 [0,043]</td><td> 2,86 [0,045]</td><td> 2,70 [0,043]</td>

<td>R value fresh (/ inch) [/ cm]^4/6</td><td> 5,31 [2,09]</td><td> 5,80 [2,28]</td><td> 5,82 [2,29]</td><td> 6,11 [2,40]</td><td> 5,82 [2,29]</td><td> 6,02 [2,37]</td><td> 6,15 [2,42]</td><td> 6,10 [2,40]</td>

<td>R value after 7 days (/ inch) Ucm]</td><td> 4,36 [1,71]</td><td> 4,63 [1,82]</td><td> 4,64 [1,82]</td><td> 4,78 [1,88]</td><td> 4,65 [1,83]</td><td> 4,84 [1,90]]</td><td> 5,01 11,97]</td><td> 4,94 [1,94]</td>

<td>Cell size, MD (mm)^7/8</td><td> 0.222</td><td> 0,181</td><td> 0,221</td><td> 0,246</td><td> 0,223</td><td> 0,212</td><td> 0,192</td><td> 0,236</td>

<td>Cell size, TD (mm) ™</td><td> 0,245</td><td> 0,224</td><td> 0,234</td><td> 0,223</td><td> 0,229</td><td> 0,197</td><td> 0,267</td><td> 0,285</td>

<td>Cell size, ND (mm)^7/8</td><td> 0,274</td><td> 0,221</td><td> 0,258</td><td> 0,259</td><td> 0,253</td><td> 0,217</td><td> 0,245</td><td> 0,250</td>

1. Wt% = wt./wt. (PSI + PS2 + PS3 + talc);

2. pph = parts of blowing agent per hundred parts (PSI + PS2 + PS3 + talc);

3. Temperature just before entering the nozzle of the foamed preparation;

4. Fresh measurements taken within 15 minutes of extrusion;

5. Determination by measurement of the diameter and nominal mass of the sample (4 "x 15" x 0.5 "(10.2 cm x 38.1 cm x 1.27 cm);

6. R is specified in ft²Hours ° F / Btu (= -0.489 cm² h ° C / J). Final resistance as determined by ASTM;

7. Cell size was determined by ASTM D3576;

8. MD, TD, and ND mean machine, lateral, and normal direction respectively;

All the foam boards in Table 2 were dimensionally stable. Measurements were made within 15 minutes of extrusion, and then after 14 and 28 days. The change, if any, was less than 1% and the overall density change from original fresh density was within 2%.

[0057] According to another aspect of the invention, an additional benefit of using methyl formate as the blowing agent is the removal of undesirable effects associated with the blowing agent in the present use, which is a further benefit of using methyl formate. Namely, the methyl formate escapes from the foam quite quickly. About 12% of the methyl formate evaporated from the 0.5 '(1.27 cm) thick board within 3 hours after extrusion and was no longer detected after 30 days using a detection limit of 500 ppm.

Since methyl formate is the only flammable component in the blowing agent blends shown in Table 2, no flame retardant is needed in the polymeric foam formulation. Ethane can be replaced by CO₂. Although ethane is a flammable compound, it also evaporates rapidly from the foam substrate which, again, does not require the use of a flame retardant.

Example C

[0058] Table 3 below shows the test results of various blowing agents used in forming insulating foam boards or boards.

Specifically, various alkenyl aromatic polymer foam sheets useful for insulation purposes were made from the comparative blowing agent and the blowing agent blends of the present invention in accordance with the extrusion process generally described herein. Comparative blowing agent blends include ethyl chloride-VOC and HAP blowing agent, in combination with non-VOC HCFC-142b co-blowing agent, and the blowing agent blend of the invention includes methyl formate, non-Voc blowing agent and non-HAP blowing agent. in combination with HCFC-142b

[0059] It should be noted that in the various examples listed in Table 3, the same devices were used and operated in exactly the same manner; the only variable was the blend of the blowing agent. Each of the alkenyl aromatic polymer foams was made in a tandem extrusion line using 1.0 inch and 1.5 inch (2.54 and 3.81 cm) single screw extruder equipped with three holes in the first extruder for injecting pressurized fluid. The effluent rate was 10 Ib / hr (4.54 kg / hr). The polymer resin used was general purpose polystyrene with a high heat of combustion and a melt flow rate of 1.6 (PSI), and the claimed polystyrene from the Applicant's commercial insulation board process, having a melt flow rate of 11.5 (PS3). About 2.0% polystyrene (PSI + PS2) was added. A flat die was used and the swellable product was directed into the mold shaping system to form foam boards with a nominal diameter of 5.0 inches (width) x 0.5 inches (thin) (12.7 cm (width) x 1.27 cm (thin). ).

[0060] Table 3 shows various examples of formulations used to make insulating foam boards from an extrudate containing polyester, talc, methyl formate and HFC-134b, according to the present invention. Also shows several comparative formulations containing polystyrene, talc, ethylene chloride, and HFC-134b. In addition, Table 3 shows the melting points of each comparative and inventive foam product before extrusion. Table 3 also shows the density, R-value, cell size of the respective planks or logs made up of the various comparative and exemplary formulations.

Π

Table 3

<td>Out.</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td>about</td><td> 2,92</td><td> 6,74</td><td> 126</td><td> 2,10 [0,033]</td>

<td>Out.</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td>o θ '</td><td> 2,61</td><td> 6,64</td><td> 126</td><td> 2,13 [0,034]</td>

<td>Out.</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td> 0,00</td><td> 2,63</td><td> 6,68</td><td> 136</td><td> 1,86 [0,030]</td>

<td>Out.</td><td> 58,00 \</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td>about θ '</td><td> 2,35</td><td> 6,06</td><td> 136</td><td> 2,12 [0,034]</td>

<td>Out.</td><td>_vol 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td>about</td><td> 2,17</td><td> 5,64</td><td> 133</td><td> 2,23 [0,035]</td>

<td>Compare</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td> 2,81</td><td> 0,00</td><td> 6,43</td><td> 126</td><td> 2,12 [0,034]</td>

<td>Compare</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td> 2,69</td><td> 0,00</td><td> 6,27</td><td> 126</td><td> 2,02 [0,032]</td>

<td>Compare</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td> 2,68</td><td> 0,00</td><td> 6,24</td><td> 127</td><td> 2,12 [0,034]</td>

<td>| Compare 1 __</td><td> 58,00</td><td> 38,00</td><td> 2,00</td><td> 2,00</td><td> 2,58</td><td>00Ό</td><td> 6,01</td><td>127 _____and</td><td> 2,29 [0,036]</td>

<td>Compare</td><td> 58,00</td><td> 38,00</td><td>oo, ri</td><td> 2,00</td><td> 2,35</td><td>about θ '</td><td> 5,48</td><td> 127</td><td> 2,31 [0,037]</td>

<td>Example</td><td>ISd</td><td>PS3 (wt%)^!</td><td>Rt &amp; g</td><td>Talc (wt%)^!</td><td>Ethyl chloride (PPh)²</td><td>Methyl Formate (PPh)²</td><td>HCFC-134b (PPh)²</td><td>Temp, top (° C)³</td><td>Fresh density (pcf)</td>

<td></td><td> 6,06 [2,38]</td><td></td><td>0.379 L.</td><td> 0,393</td><td> 0,414</td><td></td>

<td></td><td> 6,17 [2,43]</td><td> 4,95 [1,95]</td><td> 0,369</td><td> 0,474</td><td> 0,450</td><td></td>

<td></td><td> 5,71 [2,25]</td><td>o o. o. UD</td><td>CU θ '</td><td> 0,423</td><td> 0,464</td><td></td>

<td></td><td> 5,91 [2,33]</td><td> 4,69 [1,85]</td><td> 0,366</td><td> 0,399</td><td> 0,411</td><td></td>

<td></td><td>6.04 [2.38] AND</td><td>o. o</td><td> 0,304</td><td> 0,428</td><td> 0,414</td><td></td>

<td></td><td> ( 6,06 [2,37]</td><td> 4,90 [1,93]</td><td> 0,330</td><td> 0,407</td><td> 0,389</td><td></td>

<td></td><td> 6,02 ¹ [2,38]</td><td>£ oo, 7</td><td> 0,340</td><td>00 CU θ '</td><td> 0,390</td><td></td>

<td></td><td>6.06 [2.43] L. _______________</td><td> 4,91 [1,93]</td><td> 0,386</td><td> 0,482</td><td> 0,406</td><td></td>

<td></td><td> 6,13 [2,41] 1 _____________________</td><td> 4,96 [1,95]</td><td> 0,337</td><td> 0,407</td><td> 0,376 1 _______</td><td></td>

<td></td><td> 6,19 [2,43]</td><td> 4,94 [1,94]</td><td> 0,361</td><td> 0,447 _______ ________</td><td> 0,376</td><td></td>

<td>/ Ί s ο 'bb - ¹</td><td>R value fresh (/ inch) [/ cm]^4/6</td><td>R value after 7 days (/ inch) [/ cm]⁶</td><td>Cell size, MD (mm) ™</td><td>Cell size, TD (mm) ™</td><td>Cell size, ND (mm) ™</td><td></td>

Compare -Comparative Example

Wynal- An example of the invention

l. Weight% = weight composition / weight (PSI + PS3 + FR + talc);

FR = Flame Retardant

2. pph = parts of blowing agent per hundred parts (PSI + PS3 + FR + talc);

3. Temperature just before entering the nozzle of the foamed preparation;

4. Fresh measurements taken within 15 minutes of extrusion;

5. Determining the measurement of the diameter and nominal mass of the sample

4 "x 15" x 0.5 "; (10.2 cm x 38.1 cm x 1.27 cm);

6. R is specified in ft²Hours ° F / Btu (= -0.489 cm² h ° C / J). Final resistance as determined by ASTM C518;

7. Cell size was determined by ASTM D3576;

8. MD, TD, and ND mean machine, lateral, and normal direction respectively;

[0061] All the foam boards in table 3 were dimensionally stable. Measurements were made within 15 minutes of extrusion, and then after 14 and 28 days. The change, if any, was less than 1% and the overall density change from original fresh density was within 2%.

The results in Table 3 show that the non-VOC methyl formate agent can replace unsafe blowing agents such as ethylene chloride without compromising process efficiency and product characteristics such as density, cell size and R value. Therefore, the agent blends of the blowing agent according to the invention, offer significant advantages over the blowing agent currently used. While Examples B and C describe extruded boards, similar products can be made using the swellable spheres and processes shown in Figures 2 and 3 without departing from the compositions shown in Tables 2 and 3. While the present invention is described with reference to one or more In specific embodiments, many changes will be readily recognized by those skilled in the art that can be made without departing from the scope of the present invention. Each of these embodiments and their obvious variations are within the scope of the invention as claimed, which is set forth in the following claims.