CA1340708C - Cellulose based fibers and bonded composites of the fibers in polyehtylene characterized by a silane bonding agent - Google Patents

Abstract

Cellulose fibers are treated with polyethylene, anhydride, peroxide and silane or by silane in the presence of peroxide. Composites are made from cellulose fibers dispersed in a matrix of polyethylene and bonded thereto with a silane bonding agent during subsequent extrusion and or molding.

Description

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BACKGROUND OF THE INVENTION
This invention relates to composites of cellulose based fibers dispersed in a natrix of polyethylene and to treated cellulose fibers which have improved dispersability into polymer and improved adhesion thereto. More specifically) it relates to such reinforced thermoplastic composites which have good strength and molding characteristics and are derived from readily available cheap component.
The published literature includes a number of proposals which teach preparation of composites which consist essentially of thermosetting or thermoplastic resinous matrix materials having dispersed therein inorganic reinforcing Fillers, ouch as mica platelets of Flakes. Such materials are described, for example, in U.S. Patent number 3,764,456 Woodhams issued October 9, 1973; and in U.S. Patent 4,442,243 which describes such mica reinforced thermoplastic composites having improved durability, physical and aesthetic properties which are prepared by mixing the resin and the mica in the presence of propylene polymer wax. The mica may be pretreated to provide functional groups thereon Por subsequent chemical reaction with the propylene polymer wax.
The use of inorganic fillers such as mica does however present certain technical difficultie!;. Mica is a difficult material to process in making such composites. it is abrasive by nature, so that it tends to wear out processing machinery which it contacts.
The published literature contains certains references to the use of cellulosic fillers as additives for both thermoplastic and thermosetting resins. Such fillers may be derived from the finely ground products of wood pulp, the shells oP peanuts or walnuts, corn cobs) rice hulls, vegetabie fibers or certain bamboo-type reeds or grasses.
The great abundance and cheapness of such cellulosic materials in every part of the globe has made these cellulosic materials attractive sources for producing useful fillers on thermoset resins (such as the phenolics) has been :;.-..T~ _~

~' 1340708 an accepted practice for many years, their use in thermoplastics has been limited mainly as a- result of difficulties in dispersing the cellulose particles in thermoplastic melts, poor adhesion (wettability> and in conse-quence inferior mechanical properties of the molded composites.
It has been shown that the dispersion of discontinuous cellulose based fibers into polymeric matrix can be greatly improved by pretreatment of the fibers with a plastic polymer and a lubricant. U.S. Pat. no 3,943,079 to Hamed described such pretreatment. Goettler in U.S. Pat. no 4,376,144 has shown that the composites made from cellulose fibers dispersed in a matrix of plasticized vinyl chloride polymer and bonded thereto with a cyclic trimer of toluene diisocyanate can be molded or extruded to produce useful articles.
Coran et al., U.S. Pat. 4,323,625 have shown that the composites can be produced Prom grafted olefin polymers and cellulose fibers. The polyolefin have been grafted with other polymer carrying methylol phenolic groups before being combined with cellulosic fibers and bonding agent such as phenol aldehyde resin) a polyisocyanate or the like.
Lachowicz et al., U.S. Pat. 4,107,ii0 describe that a( -cellulose fibers, coated with a graft copolymer comprising 1,2 - polybutadiene to which is grafted an acryiate such as butylmethacrylate could be used in reinforcing of PE and other plastic compositions.
ao Fu,~imora et al., Jap. Pat. Kokai 137,243,178 also describe a cellulosic material which has been acetylated with gaseous acetic anhydride as a rein-forcing agent for polyolefins. -Gaylord, U.S. Pat. 3,487,777 (1969) describes compatibilization of poly-vinylchloride or polymethylmethacrylate with grafted cellulose.
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Gaylord, U.S. Pat. 3,645,939 also shows that polyethylene or polyvinyl-chloride or acrylic rubber can be compatibilized with cellulosic fibers in the presence of an ethylenically unsaturated carboxylic acid or anhydride under conditions which generate free radicals on said polymers, whereby said ethylenically unsaturated carboxylic acid or anhydride reacts with and couples with thermopiastic polymer and cellulose.

i3~0~ro8 --- Hse, U.S. Pat. 4,209,433 have treated wood material with polyisocyanate before mixing with thermosetting phenol formaldehyde resin.
Lundl et al.) U.S. Pat. 4,241,133 mixed elongated wood flakes with binder (i.e. polyisocyanate) and than hot-pressed into the form of an elongated Wadeson, Brit. Pat. 1,585,074 describe process to manufacture cellulose-polyurethane material by reaction of fibrous cellulosics with impregnated structural member as a beam, post, etc.
polyisocyanates in the presence of catalyst (zinc-octoate).
Nakavisht et al., Jap. Kokai 7697648 describe the use of cellulosics in PP.
Theiysohn et al., Ger.-Offen 2916657 present heat resistant PP molding composition. Suriyama et al., Jap. Kokai 7972247 introduce heat treated wood filler for thermoplastics. Also, Dereppe et al., Ger. Offen 2635957 as well as Kishikawa et al., Jap. Kokai 7345540 describe filler reinforced polypropy-lene.
SUMMARY OF THE INVENTION
It has now been found that the cellulosic fibers can be well compatibilize with a matrix formed by polyethylene and the adhesion to cellulosic fibers to a matrix can be substantially improved by improving the interfacial adhesion by pretreatment of the filler with a conventional silane coupling agent in the presence of a free radical source.
According to present invention, composites are made of discontinuous cellulosic fibers pre-reacted with silane bonding agent, the trade mark "A174 or A-172 or A-1100" of Union Carbide Corporation in the presence of peroxide like benzoylperoxide or t-butyl peroxide or dicumylperoxide.
Composites containing from 1 to 5096 of cellulosic fibers by weight, based on the total weight off composite are within the scope of convention.
The silane coupling agent "A-174" (gamma-methacryloxy-propyltrimethoxy silane) or "A-172" (vinyltri 2-methoxyethoxy silane> or "A-1100" (gamma-amino propyltriethoxy silane) in the presence of free-radical source is forming a :r 130'708 strong adhesive bond with wood fibers and possibly with matrix and thus provide the composite which has improved strength and stiffness.
The bonding agent has been found to be effective at relatively low concen-trations - as low as D.1 parts by weight on i00 parts of the polyethylene in the matrix. The free-radical source is used at concentration from 0.1 to 3 parts by weight based on 100 parts of the polyethylene.
The Invention also includes treated discontinuous cellulosic fibers with aspect ratio varying from 2 to 5 (saw dust), from 12 to 50 (high yield and ultra high yield pulps) and from 50 to 100 for low yield chemical cellulosic pulps bonded chemically with 1 to 10 parts of polyethylene based on fiber weight in the presence of anhydride 0.5~to 10 parts, peroxide 0.1 to 5 parts and silane varying from 0.1 to 4 parts) all weight parts related to i00 weight parts of filler. The later material has also an excellent dispersability with polyethylene matrix.
DIiTAILED DESCRIPTION OF THE INVENTION
The cellulosic material used in the invention include cellulosic fibers derived from softwood or/and hardwood pulps, i.e. chemical or mechanical or chemi-mechanist or refiner or stone groundwood or thermo-mechanical or chemi-thermomechanical or explosion or low yield or high yield or ultra high yield pulp) nut shells) corn cobs) rice hulls, vegetable fibers, certain bamboo-type reeds) grasses, bagasse) cotton, rayon (regenerated cellulose>, sawdust, wood flour) wood shavings a.nd the like.
Preferred are cellulosic fibers derived from wood sawdust, wood flour, wood pulps, e.g. mechanical pulps or chemi-thermomechanical aspen pulps. There are many available types of wood pulp which may be classified according to where they were derived by chemical or mechanical or thermal treatment or combina tion of treatments as'. well known in the pulp and paper industry. Waste pulp .. ~ei ~i or recycled pulp can also be used. The tibers have an aspect ratio (length divided by diameter).ranging from 2 to 5 Por sawdust, wood flour as well as for mechanical pulps and 15 to 50 for chemi-mechanical and chemi-thermomecha-nical pulps and 50 to 150 for low yield chemical pulps (i.e. kraft, soda or bisulfate).
In some instances) it is desirable to use mixtures of fibers having widely different aspect ratios.
The polymer contained in the matrix is described as being "polyethylene"
and includes both polyethylene polymer and copolymer of a major proportion of polyethylene with minor proportion of other copolymers like polypropylene.
The polymer "polyeth;ylene" includes linear low density polyethylene) low density polyethylene, medium density polyethylene as well as high density polyethylene) polyeth;,~lenes prepared at low and high pressures.
The cellulosic based fibers are described as "discontinuous" to distinguish from the well known incorporation of continuous cord reinforcement into rubber and plastic articles. The "matrix" is the material forming a continuous phase which surrounds the fibers. A "composite" is the combination of discontinuous fibers in a matrix wherein the contained fibers may be randomly oriented, or, to a greater or lesser degree) aligned in a particular direction.
The bonding agent '"A-174" has the formula:
CHs 0 CHz - CH - C - 0 CHs CHs CH= Si (OCHs )s gamma - methacryloxypropyltrimethoxy silane.
S h ane "A-172" has the following structure:
CH, - CH - S i ( 0 Cs H, 0 CHs )s vinyltri (2-methoxyethoxy) silane.
S h ane Union Carbide "A-1100" is gamma-Aminopropyltricthoxysilane having the formula:

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H,NC,H6 Si(OCH, CH,>, The bonding agent is used in the composites of the invention in sufficient amount to achieve an adhesive bond between the polyethylene and the cellulosic fiber. This amount can be as little as 0.1 part by weight of polyethylene up to 3 part by weight based on 100 parts by weight of polyethylene. The amount' of bonding agent required can also be expected to vary with the amount of cellulosic fibers present. The free-radical source among others is benzoyl-peroxide or d-tert-butyl peroxide in proportion varying from 0.1 to 5 parts by weight related to 100 weight parts of filler.
The precise mecanism of the silane' bonding is not known but it is highly probable that alkoxy groups hydrolyse to form silanols that react with filler and the other end of the silane coupling agent molecule) the functional organic groups (such as methacryloxy, vinyl or amino) react with the organic matrix resin as welt as organic filler. To be effective in any Given system.
the silane coupling agent must be reactive with both the matrix resin and the filler to some degree.
The coupling say be applied to the filler in a separate pre-treatment step or it may be added directly to the resin during compounding. In general, improved processing is obtained with pre-treatment in the presence of peroxi de.
Alternatively, the bonding agent may be combined with the cellulosic base fiber in pre-treatment and pre-coating step. Following the idea of Gaylord, U.S. Pat. 3,645,939) the fibers can be grafted with a silane bonding agent so as to enhance their dispersability into a composite by admixture thereto of organic polymer which can be processed as thermoplastic in an amount suffi-cient to reduce fiber°-to-fiber affinity. Preferably, the organic polymer is polyethylene, although other compatible polymer having solubility parameters at midpoint of range within one unit of that of polyethylene can be used. The pre-coating step is d:Ivided on pre-reacting of silane with cellulosic fibers in the presence of peroxide, pre-reacting of 3 to 10 weights parts of polye-~., -' 130?08 thylene based on 100 weight parts oP fiber with i - 3 parts of unsaturated oP
bicarboxylic acid (i..e. malefic anhydride) in the presence of 1 - 3 parts of peroxide) (i.e. benzo;~l-peroxide) methylethylketone peroxide, dicumyl peroxi-de, di-t-butyl peroxide, and 2.5-dimethyl - 2.5 - di(t-butyl peroxy hexane), followed by combining the products from the pre-reacting steps (celiulosic fibers silane treated plus carboylated polymer). Obtained pre-coated cellulo-sic fiber show excellent dispersability in polymeric matrix.
The ethylenically unsaturated carboxylic acid or anhydride coupling agent used in the practice oP this invention is preferably dicarboxylic such as malefic acid or anhydride) fumaric acid, citraconic acid or itaconic acid.
Malefic anhydride is i:he preferred coupling agent. Monocarboxylic acids) such as acrylic acid and methacrylic acid, may also be used.
In addition to peroxides mentined above) a more detailed compilatfon of free radical initiators which may be used is set forth at pages 11-3 to 11-51 of "Polymer Handbook", Interscience Publishers (1966).
The combining of pre-reacted product can be accomplished in an internal mixer such as a Banbury mixer, Brabender mixer, CSl-max mixing extruder or on Roll mill. The temperature of mixing is a function of mixtures and equipment used. The proportions of the ingredients are dictated by the resulting composite properties. The amount of polymer used should be high enough to ao prevent fiber to fibsrr interaction) usually at least 3 parts of polyethylene by weight per 100 party by weight of wood fibers. Usually, no more than !0 parts of polyethylensr by weight per 100 parts of fibers by weight will be used, although higher polymer level for fiber pre-coating can be employed if desired.
The fibers pre-trs~ated with silane or the one pre-coated with polymer are mixed with polymer matrix to form a composite usually in an internal mixer, extruder or an a roll. mill. Additional ingredients) such as fillers, plasti-cizers, stabilizers, colorant, etc., can also be added at this point. The following specific examples illustrate the use of silane coupling as well as grafting agent for cellulosic fibers.

1~4U'~08 EXAMPLE 1.
Materials Linear low density polyethylene (LLDPE), the trade mark "Navopol LLGR-0534-A", was supplied by Novacor Chemicals Ltd. Reported properties of LLDPE
are as follows: Melt index: 5 g/10 mfn; density: 934 kg/m'.
The chemithermomechanical pulp of aspen or birch used in this work was prepared in a Sund Defibrator and have the properties described in Table i.

PROPERTIES OF BIRCH AND ASPEN PULP
PROPERTIES BIRCH ASPEN

Drainage index (CSF), ml 117 119 Brightness) Elrepho ('K) 55.7 60.9 Opacity, (%) 94.1 91.4 Breaking length) km 4.22 4.46 Elongation (%> 1.79 1.79 Tear index, mN.m2/g 6.08 7.20 Burst, index, kPa.m2/g 1.88 2.59 Yield (%) 90.0 92.0 Kappa index No 128.0 121.7 Lignin % 18.8 17.9 ~., .

~~~.o7os The thermomechanical pulp (TMP) used in this work, prepared from a wood mixture o! 75% spruce and 25% balsam fir, was supplied by Abitibi-Paper Co.
Coupling agents i) Vinyitri (2 - Methoxy Ethoxy> silane CH= = CH - Si (0 C, H, 0 CHs >, known as ~A-172~~
ii) Gamma - methacr,yloxy - propyltrimethoxy silane CHs 0 1 I~
CH, = C - C - C - C - OCHz - CH, - CHI - Si (OCHs >s known as~~A-174~~
iii) Gamma - amino p.ropyl triethoxy silane H, N - Cs H" - Si ( OCHs - CHs >s known as ~~A-1100~~
were supplied b;r Union Carbide Company, MontrE;al.
' 30 Bonding of fibers with silanes "A-172 and A-174"
20 g of fibers, Baize Mesh 60, placed in 500 ml flask; 150 ml of carbon tetrachloride added; (0.8-2%) benzoylperoxide peroxide based on oven dried pulp weight followed with 1 to 4% of silane (by weight) "A-172" or silane "A-174". The whole mixture was heated to reflux at 70 - 75'C while agitated by magnetic stirrer for 3 hours. After cooling, CC1, was evaporated and mixture was dried at !i5'C for 24 hours.
Preearation of composLtes Mixing of polymer and fiber was performed on roll mill, C.W. Brabender Laboratory Prep. Mill, no 065. Usually 15 to 20 grams of polymer were mixed With fibers at temperatures from 155 to 160'C, the resulting mixture collected and re-mixed 5-6 timfas, then allowed to cool down to room temperature and ground to mesh size 20.
The above prepared polymer-fiber mixture was molded into the shoulder type I~;.

1340'08 test specimens) (6-24 at the same time>, in a mold, which was covered by metal plates on both sides.
The weight of material for one specimen was 0.9 g when molded at a tempera-ture of 155.5'PC for ;L5 minutes at a pressure of 3.8 MPs. The starting temperature was 93.3'1: and cooling time was 15 minutes.
!0 The samples were taken out from the mold after a 15 minute cooling period and then heat treated (annealed) at 105'C in the over for 1-2 hours, and finally allowed to stand at least 3 to 4 hours in the testing room which was kept at 23'C and 50% ~~elative humidity.
Mechanical Tests Mechanical measuresnents were made on an Instron tester (model 1131) at 23'C
and 50% RH. The rage of elongation was 100%/min in all cases. All samples were 3.175 mm in width and 6.4 cm in length (1.7 cm between grips>. The tickness of samples ways usually 0.158 cm.
Dimensions of all samples were measured with a micrometer. Ail experimen-tal date reported is an average of at least Pour measurements. Mechanical measurements of samples which have been either pre-treated in boiling water for 3 hours or tempered at -35'C in !matron Environmental Chamber Systems (model 3111>, were made on an !matron tester (model 4201). Samples) pre-treated in boiling water, were tested at 23'C and 50% RH. Mechanical proper-ties, reported for this work) are those measured at yield point. The secant modulus was evaluated from origin to yield point. The properties) measured using !matron 4201, wslre automatically calculated by HP86B using the !matron 2 412 005 General Ten=site Test Program. The chordal modulus was measured fro!e 1 to 5% strain. Average coefficients of variation for mechanical properties were as follows: stress: 3.3%; strains 4.9%; energy: 8.3%; modulus:
2. 3%.
Results in Table 2 demonstrate that CTMP aspen fibers, bonded either with silane "A-174 or A-172" were very effective in increasing the stength of resulting composites.
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EXAMPLE II
The composites were made and evaluated as in Example ( but the fibers used were not bonded with silane. Tensile data are presented in Table 3. The addition of fiber causes a sharp increase of modulus, the highest for CTMP
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Contrary the results with silane bonded fibers presented in Example I, there is sharp drop in energy as welt as elongation comparing to LLDPE values.

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EXAlIPLE Ill The composite were made and evaluated as in Example I but the silane treatment step was carried out without the presence of benzoylperoxide as follows:
Coupling agent treatment The wood libers were treated using silane coupling agents in dilute ethanol solution as follows: 0.8 g silane "A-172 or A-174" was dissolved in 15 ml of ethanol (90%> and was added by drops for 5 minutes to 20 g of aspen pulp (mesh 60), while stirring. After this addition) stirring continued for 10 minutes.
The mixture was left at 105'C in the oven to dry for 2 hours before mixing with LLDPE.
Tensile data are presented in Table 4. There isd mprovement in both stress as well as modulus when compared to polyethylene values. On the other hand, the absolute values .are inferior to that found in Table 2 where fibers were silane treated in the presence of peroxide.
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EXAMPLE IV
The composites were made and evaluated as in Example 1 but the silane treatment step was substituted by fiber impregnation with the solution of polyethylene.
lmpreanation Impregnation implies polymer deposition on fibers from polymer solution leading to physical bondage. The impregnation procedure used was as follows:
5 g of LLDPE were added to 200 ml of p-xylene and reflux with stirring (at 100'C). 25 g of untreated aspen (CTMP> 60 mesh size were added to the solution and stirred under reflux for 2 hours. The mixture was left overnight in a mechanical shaker at 20'C. The impregnated pulp was filtered and dried for 12 hours at 105'C, then for 24 hours at 55'C, and ground to 60 mesh size before being mixed with LLDPE. The polymer loading was 20%.
The tensile properties of composites filled with impregnated aspen or birch fibers are presented in Table 5. There is improvement in stress and modulus comparing to polymer matrix but deterioration in absorbed energy as well as strain values. On the other hand, these composites are considerably weaker where compared to ones presented in Example i) Table 2.
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EXAMPLE V
This time) the composites were made and evaluated as in Example 1 but the fibers were pre-coated with polymer before being mixed with polymer matrix.
The pre-coating procedures were divided in the following steps:
a) 20 g of fibers, size mesh 60, placed in 500 ml flask; + 150 ml of carbon tetrachloride; + ~:% of benzoyl peroxide (0.4 g.) followed with 1 to 4% of silane "A-1100". The whole mixture heated to reflux at 70 to 75'C while agitated by magnetic stirrer for 3 hours. After cooling, CCI, evaporated and mixture was dried at 55'C for 24 hours.
b) 2 g LLDPE placed in a round bottom flask and 100 ml of p-xylene was added +
0.1 gm of benzoyl peroxide (5% on LLDPE> + 0.2 g of maleic anhydride (10%
on LLDPE).
The whole mixture was tested under reflux while being agitated by the magnetic stirrer for 3 hours.
c) The whole content ( a + b) was put under reflux at 80-85'C, stirred for 2 hours. The content left to cool down, at room temperature, than poured in ao a centered glass funnel to filter, washed with distilled water, then dried at 105'C for 12 hours and at 55'C for 24 hours, then grinded again to the desired mesh size. Followed by mixing with LLDPE in percentages 10, 20) 30 and 40% on the roll mill as described in Example I.
The tensile results for pre-coated samples are presented in Table 6.
It is evident that pre-coating of celiulosic fibers lead to excellent adhesion between fibre and matrix and to excellent resulting properties of composition.

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The composites vere made and evaluated as in Example YI but the molding temperature varied from 154.4'C to 171.1'C. The effect of molding temperature on molding properties is presented in Table 7. The best results are obtained at 165.5'C.

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EXAMPLE VII
The composites were made and evaluated as in Example VI but molding time or pressure were varied from 5 to 20 minutes and from 2.2 to 4.34 MPa respective ly. The resulting tensile properties in Table 8 demonstrate the effect of i0 molding parameters on resulting composite properties.

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da 1340'l08 EXAMPLE VIII
The composites were made and evaluated as in Example VI but the size of cellulosic fibers was determined by mesh size used and varied from 0.09 to 1.107 milimeters and fiber aspect ratio varied from 4.7 to 46. The effect of fibre size an resulting composite properties is presented in Table 9.

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EXAMPLE IX
The composites were made and evaluated as in Example V1. In addition, the following substrates were used as polyethylene filler: The trade mark "Mica 200-NP-Suzorite" (20C1 mesh, silane treated) and supplied by Marietta Co., MontrAal. Glass fibers the trade mark "731 BA 1/32" t0.8 mm, silane treated) and supplied by Fiber Glass of Canada via Mia Chemical, Montreal.
Composites of mica or glass fiber were made using the sane procedure as used for cellulosic fiber with the exception of silane treatment since both of them have been silane treated by manufacture.
The tensile results are presented in Table 10. It is obvious that the cellulosic filled composites compare well to either mica or glass fiber composites.

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L~ k x s et ..~ l .~ 1340'08 EXAMPLE X
The composites wslre made and evaluated as in fixample UI with the exception that the mechanical properties were evaluated after composite exposure to 3 hours boiling in water) tensile properties are presented in Table lOb.
!t can be seen that the strength of grafted aspen fiber composites remained virtually unaffected by boiling and the cellulosic filled composites compared well with that of mica or glass filler.
In addition, celluilosic composites remained dimentionally as stable as mica or glass fiber composites after 35 days submersion in water at room temperate re. Water uptake after a 35 days water treatment varied from 1.9 to 3.9 percent for 20 to 40 percent fiber content respectively.
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c 130'708 The composites were made and evaluated as in Example l but the polyethylene use was LLDPE "Novapcl GF-0118-A" and the temperature of mixing on the roll mill was 1B0'C.
Tensile properties are presented in Table 11 as a function of "A-172"
concentration varying Prom 0.5 to 2% in comparison with polyethylene. The optimum improvement of both stress and modulus was achieved at 0.5% of "A-172"
used.

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2 ~ r v ~l 1 ~4~708 Exnnpl,E x 11 The composites were made and evaluated as in Example 11. Tensile proper-ties are presented i~n Table 12 for "A-174" used either with benzoyl-peroxide or di-cu0ylperoxide.

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x , 134U'~08 ao The composites were made and evaluated as in Example II but the fibers were used without silane pre-treatment. In addition) CTMP aspen composite proper-ties were compared to that of aspen sawdust tM60) or cotton cellulose (M60).
The tensile properties are presented in Table 13. It is obvious that without silane treatment there is a lost in strength expressed as stress when compared to virgin polyethylene.

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60 1V w ao ', M r r 0 0o c ;., 13~0'~08 The composites were prepared and evaluated as described in Example I but silane "A-1100" was used. In Table 14 the tensile properties of composites prepared with "A-110D" are compared to that with "A-174". It is shown that both silanes are having beneficial effect on resulting composite properties.

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f c EXEAMPLE XV
The composites were prepared and evaluated as described in Example I but medium density polyethylene the trade mark "MDPE-CIL 560B" was used as a polymer matrix. The i:ensile properties of virgin polyethylene as well as the composite are comparsrd in Table 15. An excellent adhesion between "A-172"
silane treated fibers and polymer matrix has been demonstrated by the increase of stress values for composites going from 9.5 MPa to 16 MPa at 30 weight percent of CTMP aspen wood fibers addition. In case of modulus) the values increase from 150 MPa of virgin PE to 510 MPa in case of 40% of fiber addi-tion.
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ao ~~~o~os EXAMPLE XVI
The composites were prepared and evaluated as described in Example I but the polymer matrix used was high density polyethylene the trade mark "HDPE
GRSN-8907" and fibers were mixed with polyethylene matrix in CSl-max-extruder, model CS-094 at mixing; temperature of 145'C.
Tensile properties are presented in Table 16. The reinforcing properties of CTMP aspen fibers" treated with i% of silane "A-172" are clearly demonst rated by increased stress t33.3 MPa versus 24.7 MPa for virgin HDPE> as well as by increased modulus (1647 MPa at 40 weight percent of CTHP aspen fibers present versus 966 MP~a for virgin HDPE).
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13~ X108 The composites were prepared and evaluated as in Example XVI but fn addition to silane treatment of fibers, three weight percent of PMPFIC based on HDPE, were premixed at room temperature to HDPE before the fibers were i0 mixed in CSl-max-extruder. PMPFIC is a linear polymethylene polyphenylisocya-mate of the formula:
N~'~
/\\ rGM2 I
w%
The effect of bonding isocyanate agent in addition to 1% of silane A-172 treatAent is presented in Table i6. It is obvious that the added bonding lead to further properties i4provement when comparing to silane treatment alone.
This improvement was mainly in energy (20.1 compared to 14.6 KJ x i0-° of virgin HDPE), in strelss (369 MPa compared to 24.7 MPa for HDPE) and in modulus (1556 MPa compared to 866 MPa of virgin HDPE).
Although the forel;oing invention has been described in some detail by the way of examples for purposes of clarity of understanding) it will be obvious ao that certain changes and modifications may be practised within the scope of the appended cla ms.
The embodiments of the invention in which an exclusive property or privi-lege is claimed are dfafined as follows:

Claims (29)

1. A composite of discontinuous wood cellulose fibers dispersed in a matrix comprising polyethylene wherein the fibers are chemically bonded to the matrix with silane bonding agent.

2. The composite of claim 1 wherein the bonding agent is vinyltri (2-methoxyethoxy) silane of formula:
CH2 = CH - Si (OC2H4 OCH3)3

3. The composite of claim 1 wherein the bonding agent is gamma-aminopropyltriethoxy silane having the formula:
H2N - C3H6 Si (OCH2 CH3)3

4. The composite of claim 1 wherin the bonding agent is gamma methacryloxypropyltrimethoxy silane having the formula:

5. The composite of claim 2 wherein peroxide is present.

6. The composite of claim 3 wherein peroxide is present.

7. The composite of claim 4 wherein peroxide is present.

8. The composite of claim 4 wherein polymethylene polyphenyleneisocyanate is present.

9. The composites of claims 1 wherein from 0.1 to 10 parts by weight of silane bonding agent is present, based on 100 parts of cellulose fibers by weight.

10. The composites of claims 5 to 7 wherein from 0.1 to 5 parts by weight of peroxide is present based on 100 parts of wood cellulose fibers by weight.

11. The composite of claim 8 wherein from 0.1 to 5 parts by weight of polymethylenepolyphenyleneisocyanate is present based on weight of polyethylene matrix.

12. The composites of claim 1 wherein the fibers have an aspect ratio from 2 to 150.

13. The composites of claim 1 wherein the fibers are hardwood pulp.

14. The composites of claim 1 wherein the fibers are softwood pulp.

15. The composites of claim 1 wherein the matrix contain a particulate filler.

16. The composite of claim 1 wherein the polyethylene is copolymer from a monomer mixture comprising at least fifty percent of polyethylene.

17. A composite comprising from 9 to 45% of discontinuous wood cellulose fibers dispersed in a matrix comprising from 5 to 95% by weight of polyethylene being coupled to each other by reaction with 0.1 to 10% by weight of silane rind 0.1 to 10% by weight of malefic anhydride and 0.1 to 10% by weight of peroxide.

18. The composite as defined in claim 17 wherein the silane is gamma-methacryloxypropyltrimethoxysilane of formula:

19. The composite as defined in claim 17 wherein the silane of vinyltri (2-methoxyethoxy) silane of formula:
CH2 = CH - Si (OC2H4 OCH3)3

20. The composite as defined in claim 17 wherein the silane is H2N - C3H6 Si (OCH2 CH3)3

21. The composite as defined in claim 17 wherein the fibers are softwood pulp.

22. The composite as defined in claim 17 wherein the fibers are hardwood pulp.

23. The composite as defined in claim 17 wherein the fibers have an aspect ratio from 2 to 150.

24. The composite as defined in claim 17 wherein the fiber contain a particulate filler.

25. The composites of claim 1 wherein the polyethylene is present in an amount of 10 to 90 parts by weight based on 100 parts of total composite weight.

26. The composites of claim 1 wherein the wood cellulose fiber is present in an amount from 10 to 90 parts by weight based on 100 parts of total composite weight.

27. A compression molding made from the composites of claims 1.

28. A compression molding made from the composites of claims 17.

29. An injection molding made from the composites of claims 1 and 17.