Cellulosic fiber composites

COMPOSITES CONTAINING CELLULOSE FIBER

Background of the Invention

The invention relates to composites consisting of polymers and cellulosic or lignocellulosic fibers.

Polymers are used in a variety of applications, such as food packaging. Polymer food containers are usually disposable and are then discarded.

Cellulose and ligno-cellulosic materials, which are widely produced and processed, are used in many applications. Once used, such fibers are also discarded as waste. The result is a growing waste of cellulosic or lignocellulosic fibers as well as polymers.

Summary of the Invention

In general, the invention relates to composites comprising a polymer and a textured cellulosic or lignocellulosic fiber.

The present invention relates to a composite comprising a polymer, such as a thermoplastic polymer, and at least 2% by weight, more preferably at least 5% by weight, of a texturized cellulose or lignocellulosic fiber. The invention also relates to a composite comprising polyethylene and at least about 50% by weight textured cellulose or lignocellulosic fiber.

The invention further relates to composites comprising a polymer and a textured cellulose or lignocellulosic fiber having a flexural strength of at least about 3000 psi or a tensile strength of at least about 3000 psi.

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The invention further relates to a method of making a composite comprising rupturing a cellulosic or lignocellulosic fiber to texturize the cellulose or lignocellulosic fiber and then mixing the texturized fiber with a polymer. In a preferred method, the fiber is torn by a rotary cutter. The invention also relates to a process for making composites which comprises tearing a cellulosic or lignocellulosic fiber and mixing the resulting fiber with a polymer.

As used herein, the term "textured cellulosic or lignocellulosic fiber" is intended to indicate that the fiber is substantially exposed by tearing the fiber. Of these, at least about 50%, preferably at least 70%, have a length / diameter ratio (1 / D) of at least 5, preferably at least 25 or at least 50. An example of a textured fiber is shown in FIG. I.

The composites of the invention are strong, light and inexpensive. The raw materials used to make the composites are readily available, including, for example, old (used) polymer packaging and cellulosic or lignocellulosic fiber waste.

Other features and advantages of the invention will be apparent from the description of the preferred embodiments of the invention and from the claims.

Brief description of the drawings

In FIG. Figure 1 shows a photograph of a textured newsprint sample (magnified 50 times).

Description of Preferred Embodiments

The preferred composite comprises a polymer and a cellulosic or lignocellulosic fiber.

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The polymer encapsulates cellulosic or lignocellulosic fiber and facilitates control of the composite molding process. The polymer also absorbs external stress on cellulose or lignocellulosic fiber and protects the fiber from environmental damage and structural damage. Preferred composites contain from about 20 to about 60%, more preferably from about 30 to about 50% by weight of the polymer.

Examples of polymers include polyethylene (including e.g. low-density and high-density polyethylene), polypropylene, polystyrene, polycarbonate, polybutylene, thermoplastic polyesters, polyethers, thermoplastic polyurethanes, PVC, nylon and other polymers. It is preferred that the polymers have a low melt flow index. Preferred polymers are polyethylene and polypropylene having a melt flow index less than 3 g / 10 min and more preferably less than 1 g / 10 min.

The polymers can be obtained as pure materials or obtained as waste or waste materials and are usually marketed in granular form. Preferably, the polymers are obtained as waste or waste polymers because these materials are less expensive. A preferred source of polymer is the polyethylene milk pudding used.

Textured cellulose or lignocellulosic fiber gives the composite strength.

The composite may comprise from about 30 to 90%, more preferably from 50 to 70% by weight of the texturized cellulose or lignocellulosic fiber. Examples of cellulose fiber include paper and paper products; examples of lignocellulosic fiber include wood, wood fibers and wood-related materials, as well as materials derived from hemp, grasses, rice husks, wastes from compression, cotton and jute. A preferred cellulosic fiber is newsprint. Preferred lignocellulosic fibers include jute and hemp.

Composites also contain binders. Binders promote the binding of hydrophilic fibers to hydrophobic polymers. Examples of binders include maleic anhydride-modified polyethylenes such as Fusabond® (available from Dupont, Delaware) and Polybond® (available from Uniroyal Chemical,

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Connecticut) series. A preferred binder is maleic anhydride modified high density polyethylene such as Fusabond® MB 100D.

The composites may also contain such additives as are known in the art, such as plasticizers, lubricants, antioxidants, opacifiers, thermostats, dyes, flame retardants, biocides, shock modifiers, photosensitizers, and antistatic agents.

Preparation of starting materials

If old cellulose or lignocellulosic fiber is used, it should be cleaned and dried. The cellulosic or lignocellulosic fiber must then be textured prior to mixing with the thermoplastic polymer. The fiber can be textured using any mechanical device or combination thereof. In a preferred texturizing process, the cellulose or lignocellulosic fiber is first cut into 1/4 to 1/2 oil fragments using a standard cutting device. These pieces are then torn with a rotary cutter, such as that described in Perry's Chem. Eng. Handbook, 6^thEd., P. 8-29 (1984)) and available from Sprout, Waldron Companies. The textured fiber then passes through a 2 mm sieve. Textured fiber can be stored in sealed bags. The material should be dried at approximately 105 ° C for 4 to 18 hours (until the moisture content is below 0.5%) immediately before use.

The polymer may be provided in granular or granular form and used without further purification or drying. Although the granular or granular polymer, if moisture is present, it must be dried before use.

Preparation of composites

Composites may be prepared as follows. The standard rubber / plastic blend mill is heated to 325-400 ° C. The polymer (usually in the form of granules or granules) is introduced into a heated rolling mill. After about 10 minutes, binder is added to the mill. A further 5 minutes later, the polymer / binder is added

EE 200000262 Α Textured cellulose or ligno-cellulosic fiber as a molten mixture. The latter mentioned

- ♦ '· · fiber is added in about 10 minutes.

The composite is taken from the mill, cut into sheets and cooled to room temperature. It is then molded into plates using standard injection molding techniques.

Alternatively, a mixer such as a Banbury internal mixer filled with components may be used. The components are mixed while maintaining a temperature of at least 190 ° C. The mixture is then pressed into molds.

In another embodiment, the components are mixed in an extruder, such as a Maris (Turin) TM 85 extruder equipped with rotary propellers. The polymer and binder are introduced into the extruder through a feed port. The cellulosic or lignocellulosic fiber is added to the molten polymer once it has passed about 1/3 of the length of the extruder. The extruder shall be kept at an internal temperature of at least 190 ° C. At the outlet, the composite is granulated by cutting.

Alternatively, the mixture is first prepared in a mixer, then the mixture is fed to an extruder, where it is subjected to an extrusion and a cutting granulation step.

In another embodiment, the composite is formed in the form of fibers using techniques known in the art.

Properties of composites

The finished composites consist of a network of fibers surrounded by a polymer matrix. Exposed fibers form a network structure that gives the composite strengths. Because the cellulosic or lignocellulosic fiber is textured, the surface area available for bonding to the polymer is increased compared to composites made from non-textured cellulosic or lignocellulosic fiber. The polymer binds to the surface of the exposed fibers, creating an internal blend of fibers and polymer matrix. The blending of fibers and polymer matrix adds strength to the composites.

Applications

Polymer / fiber composites are used in many applications. Composites are strong and lightweight and can therefore be used, for example, as wood substitutes.

The polymer coating gives the composites water resistance, so they can be used outdoors. For example, composites can be used to form bases that are stored outdoors for long periods of time.

Examples

Composites were prepared as follows. A standard rubber / plastic blend mill was heated to 325-400 ° C. A polymer (usually in the form of granules or pellets) was added to the preheated mill. After about 10 minutes, the polymer was attached to the rolls (i.e. the polymer melted and the melt rolled). A binder was then added to the mill. After another five minutes, the cellulose or iignocellulose fiber was added to the polymer / binder molten mixture. Said fiber was added over 10 minutes.

The composite was then removed from the mill, cut into sheets and cooled to room temperature. Portions of about 80 g were molded under pressure into plates measuring 6 x 6 x 1/8 in (15x15x0.32 cm) using standard injection molding techniques.

One composition contained the following components.

Composition No. 1

Component High density polyethylene¹Old newsprint²Binder³ (g)

160

Composition no. 1 features are as follows

240

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Bending Strength (psi) 9810 (ASTM D790)

Bending module (10⁹ psi) 6.27 (ASTM D790)

The second composition contained the following components.

Composition # 2

Component Amount (g)

High density polyethylene¹ 160

Old magazines

Binder³ 8

Composition no. 2 features are as follows.

Bending Strength (psi) 9060 (ASTM D790)

Bending module (10⁹ psi) 6.78 (ASTM D790)

Component notes: ^!Marlex 16007 ²Textured rotary cutter with 2 mm sieve ³Fusabond '~' 1 OOD

Other embodiments are within the scope of the claims.