Polyisocyanate-based adhesive

(54) Title: ADHESIVE BASED ON POLY-ISOCIANATE, MIXTURE OF REACTION TO PREPARE THE SAME, AND USE OF ADHESIVE BASED ON POLY-ISOCIANATE.

(51) Int.CI .: C08G 18/12; C08G 18/22; C08G 18/42; C08G 18/48; C08G 18/76; C09J 175/04 (30) Unionist Priority: 03/15/2007 EP 07104276.6 (73) Holder (s): HUNTSMAN INTERNATIONAL LLC (72) Inventor (s): THORSTEN GURKE; WESLEY VERBEKE (85) Date of Beginning of the National Phase: 03/09/2009 “ADHESIVE BASED ON POLY-ISOCIANATE, REACTION MIXTURE TO PREPARE THE SAME, AND, USE OF ADHESIVE BASED ON POLY-ISOCIANATE”

The present invention relates to adhesive compositions and adhesives based on polyisocyanate, adhesive formulations based on polyisocyanate and reactive mixtures for the preparation of such adhesives.

Adhesives based on compounds containing one or more isocyanate group per molecule and on compounds containing more than one hydroxyl group per molecule, so called polyurethane adhesives or polyisocyanate based adhesives, are used in many areas of application due to its remarkable properties, its simple and economical processing and its high resistance. One of these areas of application is flexible packaging where a laminated film or sheet is used, produced using an adhesive.

However, for some applications, the crosslink density of standard polyurethane adhesives is very low, preventing the material from being used in severe climatic conditions. For example, car body adhesives must have high resistance to salt water and high heat.

For other applications, such as flexible food packaging, the curing rate of polyurethane adhesives is very low, requiring prolonged storage of the final laminate to reduce the amount of aromatic aromatic amines below the legally required limit.

For adhesives in general, a good and permanent bond to the substrate or substrates to which it is added is sought. The applied adhesives may fail according to at least two failure modes. According to a first failure mode, the adhesion between the adhesive and the surface of the substrate on which the adhesive adheres is broken. This failure mode is also referred to as adhesive failure or adhesion failure. According to a second failure mode, the adhesive itself breaks under the stress produced on the adhesive, for example, through the mutual displacement of the two substrate surfaces that are held together by the adhesive. This failure mode is also referred to as cohesion failure.

For both cohesion and adhesion failures, the maximum stress that the adhesive can resist is indicative of the bond strength provided by the adhesive. The higher the maximum tension that the adhesive can resist, the stronger the bond and the better the cohesion, or the failure of adhesion can be avoided.

An objective of the invention is to present a strong adhesive, suitable to withstand the maximum increasing stresses. It is yet another object of the present invention to provide an adhesive or adhesive composition based on polyisocyanates experiencing one or more of the above mentioned disadvantages to a certain extent, or even not experiencing one or more of the above mentioned disadvantages.

Some adhesives according to the embodiments of the present invention produce bonds suitable for use in more climatic conditions, such as at high temperature or in saline conditions, for example, car body adhesives subjected to high heat and / or salt water .

Some adhesives in accordance with the embodiments of the present invention produce bonds suitable for use in flexible food packaging, due to a reduction in the migration of aromatic amines, ie, a migration rate below the legally required limit.

According to a first aspect of the present invention, a polyisocyanate based adhesive is presented, the adhesive of which is prepared by reacting an organic polyisocyanate with a compound containing isocyanate-reactive hydrogen atoms in the presence of a trimerization catalyst .

The presence of a trimerization catalyst has the effect of the polyisocyanate based adhesive according to the present invention to become a polyisocyanurate based adhesive.

Some embodiments of the polyisocyanate-based adhesives according to the present invention have the benefit of extremely fast curing and therefore resistance to rapid handling. In addition, some embodiments of the polyisocyanate-based adhesives according to the present invention have an extremely high cross-linking density (compared to currently known polyurethane-based adhesives), which increases bond strength as well as strength against an unfavorable environment and sliding. The increased strength also results in a higher maximum stress than the adhesive can resist before cohesion or adhesion failure occurs. Some embodiments of the polyisocyanate-based adhesives according to the present invention achieve a faster reduction in the presence and / or migration of aromatic amines in the cured film, which is extremely valuable when the adhesive is used in food-related applications and in medicine.

Organic polyisocyanates may be aromatic or aliphatic organic polyisocyanates.

The organic polyisocyanate used in the present invention may consist of any number of polyisocyanates, including, but not limited to, isocyanates of the type toluene diisocyanates (TDI), diphenylmethane diisocyanate (MDI), and prepolymers of these isocyanates. Preferably, the polyisocyanate may have at least two aromatic rings in its structure, and is a liquid product. Polymeric isocyanates having a functionality greater than two are preferred.

The functionality of an organic polyisocyanate, as such or as polymeric or prepolymeric polyisocyanates, refers to the average number of isocyanate groups per molecule, averaging over a statistically relevant number of molecules present in organic polyisocyanate.

In the case where a diphenylmethane diisocyanate (also known as methylene diphenyl diisocyanate, and referred to as MDI) is used to produce an adhesive according to the present invention, the diphenylmethane diisocyanate (MDI) used in the present invention may be in the form of its isomers 2 , 4 2.2 and 4.4 '- and mixtures thereof, mixtures of diphenylmethane diisocyanates (MDI) and oligomers of the same known in the art as crude or polymeric MDI (polymethylene polyphenylene polyisocyanates) having an isocyanate functionality greater than 2, or any of its derivatives having a group of urethane, isocyanurate, allophonate, biuret , uretonimine, uretdione and / or iminooxadiazinedione and mixtures thereof.

Examples of the other suitable organic polyisocyanates are tolylene diisocyanate (also known as toluene diisocyanate, and referred to as TDI), such as 2.4 TDI and 2.6 TDI and any suitable mixture of isomers, hexamethylene diisocyanate (HMDI or HDI), isophorone diisocyanate (IPDI), butylene diisocyanate, trimethyl hexamethylene diisocyanate, di (cyclohexyl isocyanate) methane, such as 4,4'-dicyclohexyl methane 4,4'-diisocyanate (H12MDI), methyl isocyanate-1,8-octane diisocyanate and tetramethylxylene diisocyanate (TMXDI), 1,5-naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), 1,4-cyclohexane diisocyanate (CDI), tolidine diisocyanate (TODI ), any suitable mixture of these organic polyisocyanates, and any suitable mixture of one or more of these organic polyisocyanates with MDI in the form of their 2,4'-, 2,2 and 4,4 isomers and mixtures thereof, mixtures of diphenylmethane diisocyanates (MDI) and oligomers thereof.

The preferred organic polyisocyanates used for the present invention are polymeric or prepolymeric organic polyisocyanates, such as quasi-prepolymers, semi-prepolymers or whole prepolymers, which could be obtained by reacting the polyisocyanates, for example , organic polyisocyanates as presented above, and preferably, organic polyisocyanates based on MDI, with compounds containing isocyanate-reactive hydrogen atoms. Polymeric organic polyisocyanates are to be understood as polyisocyanate compounds having an isocyanate value of less than 6.5%. Whole prepolymers based on organic polyisocyanates should be understood as polyisocyanate compounds having an isocyanate value that varies between 6.5 and 12%. Semi-prepolymers are to be understood as polyisocyanate compounds having an isocyanate value that varies between 12 and 22%. Quasi-prepolymers are to be understood as polyisocyanate compounds having an isocyanate value that varies between 22 and 28%. It should be understood that other polyisocyanates can also be used, having isocyanate values ​​greater than 28%. The isocyanate content, the isocyanate value or the NCO value means the proportion, expressed as a percentage, of the molar mass of the isocyanate groups in the isocyanate or in the polyisocyanate component in relation to the total molar mass of the isocyanate or in the poly- isocyanate.

Examples of compounds containing isocyanate-reactive hydrogen atoms suitable for producing polymeric or prepolymeric polyisocyanates, include alcohols, glycols or even polyether polyols of relatively high molecular weight of polyester polyols, mercaptans, carboxylic acids, such as polyacid acids basic, amines, urea and amides. Especially suitable polymeric or prepolymeric polyisocyanates are reaction products of polyisocyanates with monohydric or polyhydric alcohols.

Polymeric or prepolymeric polyisocyanates are prepared by conventional methods, for example, by the reaction of polyhydroxyl compounds that have a molecular weight of 400 to 5000, especially, mono- or polyhydroxy polyethers , optionally mixed with polyhydric alcohols that have a molecular weight of less than 400, with excess amounts of polyisocyanates, for example, aliphatic, cycloaliphatic, aromatic or heterocyclic araliphatic polyisocyanates.

Examples of polyether polyols are polyethylene glycol, polypropylene glycol, copolymer of polypropylene glycol ethylene glycol, polytetramethylene glycol, polyiexamethylene glycol, polyheptamethylene glycol, polydecamethylene glycol, and polyether polyols obtained by copolymerization of alkylene oxide ring. such as ethylene oxide and / or propylene oxide, with isocyanate reactive initiators of functionality 2 to 8. The functionality of isocyanate-reactive initiators should be understood as the number of hydrogen atoms reactive to isocyanate per initiator molecule. The polyester diols obtained by reacting a polyhydric alcohol with polybasic acid are presented as examples of polyester polyols. As examples of polyhydric alcohol, ethylene glycol, polyethylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9nonanediol, 2-methyl-1,8, octanediol, and the like , can be displayed. Examples of polybasic acid include phthalic acid, dimer acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, and the like. The preferred polyols to be used in polymeric or prepolymeric polyisocyanates are polyols that improve the miscibility of the polyol with the organic polyisocyanate, for example, using polyols consisting of a high content of ethylene oxide. The term miscibility should be understood as being capable of mixing without separation into two or more phases. It should be understood that the components must be miscible within the applicable proportion.

In an especially preferred embodiment of the invention, polymeric or prepolymeric polyisocyanates can be used as the polyisocyanate component having an average functionality of 2 to 2.9, preferably 2.0 to 2.5, an maximum viscosity of 6000 mPas, and an isocyanate content (or NCO value) of 6 to 30% by weight, preferably 10 to 26% by weight. Viscosity is measured using a Brookfield viscometer (model DVII) with a spindle 21 at a temperature of 25 ° C.

The second component in current adhesive formulations is an isocyanate-reactive compound. As an example, any of the aforementioned compounds containing isocyanate-reactive hydrogen atoms which are suitable to produce the applicable prepolymers, can be used.

The best adhesive performance is achieved when both the components, the polyisocyanate and the isocyanate reactive compound, are easily miscible with each other. In this respect, good miscibility means a clear solution after a good mix. Again, the term miscibility should be understood as being capable of mixing without separation into two or more phases. It should be understood that the components must be miscible within the applicable proportion.

According to the present invention, at least one of the compounds containing isocyanate-reactive hydrogen atoms and the organic polyisocyanate, constitute at least one, and optionally more than one soft block. It was observed that the soft block content of the adhesive has an influence on the adhesive performance. The polyisocyanate based adhesives according to the present invention may have a soft block content between 20 and 70% by weight, more preferably between 40 and 60% by weight. It has been found that adhesives according to the present invention having a soft block content in the range of 20% to 70%, especially in the range of 40% to 60%, may show a reduced release of aromatic amine.

The soft block content is defined as the weight percentage of isocyanate-reactive compounds present as such and / or if applicable, present in the prepolymer, which have a molecular weight (also referred to as MW) above 500. The percentage by weight is expressed in relation to the weight of the entire adhesive formulation.

Therefore, a prepolymer can be used, which itself has a soft block content, for example, a relatively high soft block content and / or an amount, for example, a high amount of an isocyanate-reactive compound. , having an MW greater than 500.

The soft blocks may therefore be supplied by the compound containing isocyanate-reactive hydrogen atoms, and / or if applicable, compounds containing isocyanate-reactive hydrogen atoms used for the production of polyisocyanate prepolymers, in the case of polyisocyanate organic is a polyisocyanate prepolymer.

The soft blocks can be supplied completely by the compound containing hydrogen atoms reactive to isocyanate being a component of the adhesive formulation. The soft blocks can be produced completely by compounds that contain isocyanate-reactive hydrogen atoms used to produce the polyisocyanate prepolymers. The soft blocks may be produced partially by the compound containing isocyanate-reactive hydrogen atoms being a component of the adhesive formulation, and partially, by the compounds containing isocyanate-reactive hydrogen atoms used to produce the polyisocyanate prepolymers. Preferably, at least 50% of the soft block content, that is at least half of the total mass produced by the soft block content, is supplied by the adhesive formulation component, the component of which produces the isocyanate-reactive hydrogen atoms for the adhesive formulation. .

The third component of the current adhesive formulation is a catalyst that promotes the trimerization of isocyanates from the organic polyisocyanate that is part of the adhesive.

As a trimerization catalyst, all those catalysts known as tetraalkylammonium hydroxides (for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrabutylammonium hydroxide), weak organic acid salts (eg, tetramethylammonium acetate, tetraethylammonium acetate) and acetate tetraethylammonium acetate) , and trialkylhydroxyalkylammonium hydroxides (e.g., trimethylhydroxypropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, triethylhydroxypropylammonium hydroxide and triethylhydroxyethylammonium hydroxide), weak organic acid salts (for example, trimethylhydroxypropylammonium acetate, trimethylhydroxyethylammonium acetate, triethylhydroxypropylammonium acetate and triethylhydroxyethylammonium acetate, for example, tertiary amines, tertiary amines , 1,5-diaza-bicycles [4.3.0] noneno-5,1,815 diazabicycles [5.4.0] -undecene and 2,4,6-tris (dimethylaminomethyl) phenol), metal salts of alkyl carboxylic acids (e.g., acetic acid, caprylic acid, caprylic acid, octylic acid, myristic acid and naphthenic acid), and the like, and combinations of two or more of such catalysts.

According to the preferred embodiments of the present invention, a trimerization catalyst or catalysts of the group of alkali metal salts of carboxylic acids, such as potassium acetate or potassium 2-ethylexanoate, can be used.

The amount of trimerization catalyst used may be in the range, for example, 0.01% by weight to 0.1% by weight, preferably between 0.02 and 1% by weight, based on the total formulation, plus preferably, between 0.02 and 0.50% by weight, as in the range of 0.1 to 0.2% by weight.

Preferably, the catalyst can be dissolved in the isocyanate-reactive compound to obtain storage stability.

Adhesive compositions according to the present invention may include other optional components, such as additives typically used in adhesive compositions, such as, for example, wetting agents, dispersing aids, thickeners, surfactants, pigments, mineral fillers, adhesion promoters (such as as compounds containing silanyl groups), foaming agents and anti-microbial agents.

According to a second aspect of the present invention, a reaction mixture for preparing a polyisocyanate based adhesive is provided. The reaction mixture is composed of an organic polyisocyanate, a compound containing isocyanate-reactive hydrogen atoms and a trimerization catalyst.

A reaction mixture according to the second aspect of the present invention may be suitable for producing an adhesive according to the first aspect of the present invention.

The elements of the reaction mixture, ie, organic polyisocyanates, compounds containing isocyanate-reactive hydrogen atoms and trimerization catalysts may be similar, even identical, as corresponding elements added to the polyisocyanate based adhesive according to first aspect of the present invention.

A reaction mixture according to the present invention may have a soft block content between 20 and 70% by weight, more preferably between 40 and 60% by weight.

The soft block content is defined as the percentage by weight of isocyanate-reactive compounds present as such, and if applicable, present in the prepolymer, which has a molecular weight (also referred to as MW) above 500. The percentage by weight is expressed in relation to the weight of the total formulation of the reaction mixture.

Therefore, a prepolymer can be used, which itself has a soft block content, for example, a reasonably high soft block content and / or an amount, for example, a high amount of a reactive compound the isocyanate having an MW greater than 500.

The soft blocks may therefore be supplied by the compound containing isocyanate-reactive hydrogen atoms, and / or if applicable, the compounds containing isocyanate-reactive hydrogen atoms used to produce the polyisocyanate prepolymers, in the case of the polyisocyanate organic is a polyisocyanate prepolymer.

The soft blocks can be supplied completely by the compound containing hydrogen atoms reactive to isocyanate being a component of the reaction mixture. The soft blocks can be produced entirely by compounds containing isocyanate-reactive hydrogen atoms used for the production of polyisocyanate prepolymers. The soft blocks can be produced partially by the compound containing isocyanate-reactive hydrogen atoms being a component of the reaction mixture, and partially, by the compounds containing isocyanate-reactive hydrogen atoms used to produce the polyisocyanate prepolymers. Preferably, at least 50% of the soft block content, that is, at least half of the total mass produced by the soft block content, is produced by the reaction mixture component, whose component produces the isocyanate-reactive hydrogen atoms in the mixture of the reaction.

According to a third aspect of the present invention, the polyisocyanate based adhesive according to the first aspect of the present invention is used to produce a structural adhesive.

According to a fourth aspect of the present invention, the polyisocyanate based adhesive according to the first aspect of the present invention is used to produce a laminated film.

Organic polyisocyanate, the isocyanate-reactive compound,

ie, the compounds containing hydrogen atoms reactive to isocyanate, and the trimerization catalyst, are mixed and the reaction mixture is used to produce an adhesive, for example, an adhesive layer of a laminated structure constituting a support structure, a second substrate layer and an adhesive layer that connects the support layer on the second substrate layer. The adhesive layer can be supplied, for example, by coating the reaction mixture on a support structure, such as a film.

As an applicator for the adhesive according to the present invention, known applicators can be mentioned, such as an airless spraying machine, an air-spraying machine, dipping, roller coating, brush and the like.

The conditions used to cure an adhesive layer, after coating the reaction mixture on a support structure, for example, a film, and to produce a second layer of substrate during lamination using an adhesive according to the invention, preferably , are 20 to 150 ° C, especially preferably 60 to 100 ° C. In the production of a laminated structure, for example, a laminated film, using the present adhesive, the film used as a support structure and / or the second substrate layer, are not critical. With respect to the film, a polyester type film, such as polyethylene terephthalate or the like, may be mentioned; a polyolefin-type film, such as polyethylene, polypropylene or the like; or a polyamide type film, such as nylon or the like; a metallic blade such as an aluminum blade, a copper blade or the like; a copolymer of ethylene vinyl acetate or a product of its saponification; a cellophane; a polyvinyl chloride, a polyvinylidene chloride; a polystyrene; A paper; and so on. Stressed and surface-treated products can also be used appropriately (for example, products of the same (for example, corona discharge treated or coated on the surface).

The adhesive of the present invention can be used appropriately for lamination, not only between two layers of film but also between three or more layers of film.

The various aspects of this invention are illustrated, but are not limited by the following examples.

In these examples, the following ingredients were used;

As the organic component of polyisocyanate:

SUPRASEC 1004: MDI variant of NCO value 32.8%, available from Huntsman Polyurethanes (0.6% soft block content);

SUPRASEC 1007: prepolymer of NCO value 6.8, based on MDI and polyether polyol with MW 6000, available from Huntsman Polyurethanes (75.1% soft block content);

SUPRASEC 1306: 4,4-MDI, available from Huntsman Polyurethanes (0% soft block content);

SUPRASEC 1412: prepolymer of 19% NCO value, based on MDI and MW 2000 polyester polyol, available from Huntsman Polyurethanes (soft block content 37.0%);

SUPRASEC 2004: MDI variant of NCO value 32.8%, available from Huntsman Polyurethanes (0.6% soft block content);

SUPRASEC 2008: prepolymer of 10.2% NCO value, based on MDI and MW 4000 polyether polyol, available from Huntsman Polyurethanes (soft block content 65.47%);

SUPRASEC 2020: MDI variant of NCO value 29.6%, available from Huntsman Polyurethanes (soft block content 0%);

SUPRASEC 2024: prepolymer of 23% NCO value, based on MDI and MW 125 polyether polyol, available from Huntsman Polyurethanes (0% soft block content);

SUPRASEC 2026: prepolymer of NCO value 21.4%, based on the mixture of MDI and a mixture of polyether polyol, available from Huntsman Polyurethanes (22.3% soft block content);

SUPRASEC 2029: prepolymer of NCO value 24.5%, based on MDI and on a polyether polyol with MW 125, available from

Huntsman Polyurethanes (0% soft block content);

SUPRASEC 2045: prepolymer of NCO value 16%, based on MDI and polyether polyols with MW 125 and 2000, available from Huntsman Polyurethanes (soft block content around 42.53%);

SUPRASEC 2054: prepolymer of NCO value 15%, based on MDI and a polyether polyol with MW 2000, available from Huntsman Polyurethanes (soft block content 48.7%);

SUPRASEC 2058: prepolymer of NCO value 15.4%, based on MDI and a polyether polyol of MW 2000, available from Huntsman Polyurethanes (soft block content 47.9%);

SUPRASEC 2060: prepolymer of NCO value 16%, based on MDI and a polyether polyol of MW 2000, available from Huntsman Polyurethanes (soft block content 44.3%);

SUPRASEC 2067: prepolymer of NCO value 19.3%, based on MDI and a polyether polyol of MW 2000, available from Huntsman Polyurethanes (soft block content 35.9%);

SUPRASEC 2344: prepolymer of NCO value 15.5%, based on MDI and polyether polyols of MW 2000 and 2400, available from Huntsman Polyurethanes (soft block content 48%);

SUPRASEC 2405: prepolymer of NCO value 28.8%, based on MDI and a polyether polyol of MW 750, available from Huntsman Polyurethanes (soft block content 3%);

SUPRASEC 2496: MDI variant of NCO value 31.3%, available from Huntsman Polyurethanes (soft block content 0%);

SUPRASEC 2642: NCO MDI variant of 32.7% NCO value, available from Huntsman Polyurethanes (0% soft block content);

SUPRASEC 3030: a mixture of 70% by weight of 4,4-MDI and 30% by weight of 2,4-MDI, available from Huntsman Polyurethanes (0% soft block content);

SUPRASEC 3050: a mixture of 50% by weight of 4,4-MDI and 50% by weight of 2,4-MDI, available from Huntsman Polyurethanes (0% soft block content);

SUPRASEC 4102: MDI variant of NCO value 29.6%, available from Huntsman Polyurethanes (0% soft block content);

Examples of components containing hydrogen atoms reactive to isocyanate are:

DALTOCEL F444: MW 4360 polyether polyol, available from Huntsman Polyurethanes:

DALTOCEL F456: MW 2000 polyether polyol, available from Huntsman Polyurethanes:

DALTOCEL F526: MW 1300 polyether polyol, available from Huntsman Polyurethanes:

DALTOLAC R 251: MW 673 polyether polyol, available from Huntsman Polyurethanes;

DALTOREZ P775: MW 2500 polyether polyol, available from Huntsman Polyurethanes;

Poli BD 45 HTLO: MW 2800 polybutadiene polyol, available from Sartomer:

An example of a suitable trimerization catalyst is the LB catalyst, ie, a metal salt trimerization catalyst available from Huntsman Polyurethanes. Potassium hydroxide is also an example of a trimerization catalyst.

SUPRASEC, DALTOLAC, DALTOREZ and DALTOCEL are trademarks of Huntsman International LLC.

EXAMPLE 1

In this example, the influence of the miscibility of the system on the adhesive resistance was tested.

In one test SUPRASEC 2029 was cured with the different polyols shown in Table 1 below in a 50:50 weight ratio in the presence of the LB catalyst in an amount of 0.2% by weight.

The maximum stress (in MPa) was determined according to the standard EN 204 - 205.

Miscibility was determined by visual inspection and classified as shown in table 1, where + indicates a clear solution after a good mix and indicates an unclear solution after a good mix.

Table 1

<td>Pnlinl</td><td>Miscibility</td><td>Maximum voltage</td>

<td>DALTOCEL F444</td><td> +</td><td> 9,8</td>

<td>DALTOCEL F456</td><td> +</td><td> 8</td>

<td>Poly BD 45 HTLO</td><td> -</td><td> 6,8</td>

<td>DALTOREZ P775</td><td> -</td><td> 1,7</td>

In a similar test, SUPRASEC 2024 was used in place of SUPRASEC 2029. The results (with the same meaning as applicable for table 1) are shown in table 2.

Table 2

<td>1 ····· 'X PoHol</td><td colspan="2">Miscibility l · 'Maximum tension</td>

<td>DALTOCEL F444</td><td> -</td><td> 0,3</td>

<td>DALTOCEL F456</td><td> +</td><td> 10</td>

<td>Poly BD 45 HTLO</td><td> -</td><td> 4,6</td>

<td>DALTOREZ P775</td><td> +</td><td> 8,5</td>

Both of these tests show that miscibility has a significant impact on the system's performance as an adhesive.

EXAMPLE 2

This example is intended to provide information on the influence of the soft block content on the adhesion properties.

Screening of several commercially available polyisocyanates 20 from Huntsman in combination with DALTOCEL F444, with a weight ratio of 19: 1 (100 bp of polyisocyanate and 5 bp of polyol).

The two components were mixed in the presence of the LB catalyst in an amount of 0.2% by weight, and applied as an adhesive to an 80 μ thick steel / steel joint which was subsequently cured in an oven at 80 ° C for 1 hour. After cooling and conditioning to normal weather conditions, the adhesion properties were measured according to the standard EN 204 - 205. Cohesion failure (CF) means that the cohesive resistance, ie, the resistance of the adhesive layer itself, is less than the interfacial resistance between the adhesive and the substrate, in this specific case, the steel surface, at the interface between the adhesive and the substrate. The adhesive layer will be broken, leaving the adhesive on the two surfaces of the two substrates on which the adhesive must be adhered.

Adhesion failure (AF) means that the cohesive resistance, ie, the resistance of the adhesive layer itself, is greater than the interfacial resistance between the adhesive and the substrate, in this specific case the steel surface, at the interface between the adhesive and the substrate. The bond on one of the substrate surfaces between the substrate surface and the adhesive will be broken, leaving adhesive only on one of the surfaces of the two substrates on which the adhesive is to be adhered. AF and CF are terms for evaluation when measuring adhesion of the specimen.

The results are shown in table 3. The soft block content of the formulation is also indicated.

Table 3

<td>Polyisocyanate</td><td>Soft block (% weight)</td><td>........................, ... . J _ ..................._z.... .........</td><td></td>

<td>SUPRASEC 2020</td><td> 4,8</td><td> 1,4</td><td>AF</td>

<td>SUPRASEC 2496</td><td> 4,8</td><td> 1,7</td><td>CF</td>

<td>SUPRASEC 2642</td><td> 4,8</td><td> 1,6</td><td>CF</td>

<td>SUPRASEC 3050</td><td> 4,8</td><td> 1,2</td><td>CF</td>

<td>SUPRASEC 4102</td><td> 4,9</td><td> 1,6</td><td>AF</td>

<td>SUPRASEC 1004</td><td> 5,3</td><td> 1,5</td><td>CF</td>

<td>SUPRASEC 2004</td><td> 5,3</td><td> 1,5</td><td>CF</td>

<td>SUPRASEC 2405</td><td> 7,6</td><td> 1,4</td><td>CF</td>

<td>SUPRASEC 2024</td><td> 14,8</td><td> 1,8</td><td>AF</td>

<td>SUPRASEC 2026</td><td> 27,3</td><td> 4,6</td><td>AF</td>

<td>SUPRASEC 1412</td><td> 40,4</td><td> 11,6</td><td>AF</td>

<td>SUPRASEC 2060</td><td> 47</td><td> 11</td><td>CF</td>

<td>SUPRASEC 2058</td><td> 50,4</td><td> 10,6</td><td>CF</td>

<td>SUPRASEC 2344</td><td> 50,5</td><td> 10</td><td>AF</td>

<td>SUPRASEC 2054</td><td> 51,1</td><td> 10,2</td><td>CF</td>

<td>SUPRASEC 2008</td><td> 67,1</td><td> 4,1</td><td>AF</td>

<td>SUPRASEC 1007</td><td> 76,3</td><td> 1,2</td><td>AF</td>

The increased maximum stress is noted for the soft block content in the range of 20% by weight to 70% by weight, with an optimum in the range of 40 to 60% by weight of soft block content.

EXAMPLE 3

Here too, the influence of the soft block content on the adhesive strength was tested, adding various amounts of DALTOCEL F444 in SUPRASEC 2029 in the presence of the LB catalyst in an amount of 0.2% by weight (in relation to the total weight of the formulation adhesive). The isocyanate / polyol ratio in table 4 means a weight ratio of x parts by weight of SUPRASEC 2029 to the parts by weight of y of DALTOCEL F444.

Table 4

<td>· · Relationship ·</td><td>Soft block (%</td><td>Maximum voltage (MFa)</td><td>Failure-</td>

<td> 19/1</td><td> 9,7</td><td> 3,4</td><td>AF</td>

<td> 3/1</td><td> 28,7</td><td> 4,1</td><td>AF</td>

<td> 1/1</td><td> 52,6</td><td> 10,3</td><td>CF</td>

<td> 0,5/1</td><td> 68,4</td><td> 2,7</td><td>AF</td>

It is clear that the soft block content influences the maximum stress that the adhesive can resist before failure. Preferred soft block contents are in the range of 20% to 70%, more preferably in the range of 40% to 60%.

EXAMPLE 4

This example shows an improvement in the cure rate between the polyisocyanate based adhesive system, being a polyisocyanurate based adhesive system according to the present invention, and the prior art polyurethane based adhesives.

SUPRASEC 1306, SUPRASEC 3030 and SUPRASEC 3050, each is reacted with polypropylene glycol with MW 2000 (PPG2000) to obtain polyisocyanate prepolymers with an NCO value of 16% by weight. Table 5, second and third columns, shows the relationship between the two components, which are reacted to produce the pre19 polymers. SUPRASEC 2045 and SUPRASEC 2344 are also polyisocyanate prepolymers. Those prepolymers were cured with castor oil (prepolymer / castor oil ratio 105: 100) for 10 days in normal weather producing a film. Subsequently, the films obtained were stored for 10 days at 50 ° C in an acidic solution (3% acetic acid in an aqueous solution). The solution was subjected to analytical analysis to determine the remaining aromatic amines (DADPM).

The results are shown in table 6, (where S refers to SUPRASEC).

Table 5

<td>\ Prepolymer: '' 'Components. *. * 3 »&gt; · * ** · *“ * t * ·</td><td>% - 'pesp.de: \ soft blocks</td><td>% by weight of pdiisoldanâító. 'free (MDI) in the</td><td>DADPMrestant WfcL · THERE.</td>

<td>S 1306 + PPG 2000</td><td> 58,2</td><td> 41,8</td><td> 7</td>

<td>S 3030 + PPG 2000</td><td> 58,2</td><td> 41,8</td><td> 23</td>

<td>S2045</td><td> 42,5</td><td> 41,8</td><td> 26</td>

<td>S 3050 + PPG 2000</td><td> 58,2</td><td> 41,8</td><td> 16</td>

<td>S2344</td><td> 48,0</td><td> 39,5</td><td> 10</td>

These results show that only part of the standard polyurethane-based adhesives meet the legal requirement for a maximum migration of 20 ppb of aromatic amines, even after 10 days of curing. The system based on SUPRASEC 2344 meets the legal requirements but a minimum of 10 days of storage is required; the measurement after 7 days of storage produced 72 ppb of aromatic amines.

In comparison, the polyisocyanurate based adhesives according to the present invention have been evaluated for their decline in aromatic amine emission. SUPRASEC 1412 and SUPRASEC 2344 were used respectively as the polyisocyanate and were both cured with DALTOLAC R 251 and DALTOCEL F 526 (DALTOLAC R 251 and DALTOCEL F526 used in a 4/1 weight ratio). The weight ratio between SUPRASEC 2344 and the combined weight of DALTOCEL F526 and DALTOLAC is equal to 4: 1). DALTOCEL F526 includes 0.01% potassium hydroxide. The melts were cured for 30 minutes at 80 ° C, cooled to room temperature and within 4h were stored for 10 days at 50 ° C in the test solution mentioned above. Subsequently, the amount of aromatic amines was determined in the solution.

For the system based on SUPRASEC 1412 the result was 13.5 ppb of aromatic amines, and for the system based on SUPRASEC 2344 the amount of aromatic amines was 12.7 ppb. As such, both systems met legal requirements within one day of processing. This results in a reduction in the curing time, and therefore, in a great cost saving in the reduction of working capital and stock, when these adhesives are used for the production of laminated films for use in the food industry.

In another example, as shown in table 6, SUPRASEC 2344 was reacted with a polyol being castor oil (isocyanate index 105) to produce the polyisocyanate adhesive according to the prior art (formulation (A)), or with a polyol in the presence of a trimerization catalyst, both producing an adhesive with a soft block content in the preferred range of 20% to 70% (formulation (C)), and another with a soft block content not within this preferred range (formulation (B)).

The amount of release of aromatic amines (DADPM) was determined in an identical manner to that presented above.

Table 6

<td>IkOS »</td><td></td><td></td><td>DADPM later - · &lt;·? ·. v&gt; x. ·</td>

<td>(A) S2344 + castor oil</td><td> 58</td><td> 204</td><td> 27</td>

<td>(B) S2344 + Daltolac R251 / Daltocel F526 (1/1 iso / poly.iol ratio) + cat. trimerization</td><td> 74</td><td> 160</td><td> 22</td>

<td>(C) S2344 + Daltolac R251 / Daltocel F526 (4/1 iso / polyol ratio) + cat. trimerization</td><td> 58</td><td> 13</td><td> 5</td>

This example also shows that the production of a polyisocyanate-based adhesive consisting of a trimerization catalyst (thereby producing a polyisocyanurate-based adhesive), with a soft block content in the preferred range of 20% to 70%, more preferably, within the range of 40% to 60%, causes the release of the aromatic amine to be significantly reduced.

Again, the use of these adhesives results in a reduction in the curing time, and therefore, a great cost saving in the reduction of working capital and stock, when these adhesives are used to produce laminated films for use in the food industry.