CA1334558C - Cellulose based fibers and bonded composites of the fibers in polystyrene polymers characterized by an isocyanate bonding agent - Google Patents

Abstract

Composites are made from cellulose fibers dispersed in a matrix of polysty-rene and an isocyanate and bonded thereto during subsequent extrusion and/or molding.

Description

CELLULOSE BASED FIBERS AND BONDED COM~O~llr~ OF THE FIBERS
IN POLYSTYRENE POLYMERS CHARACTERIZED BY AN ISOCYANATE BONDING AGENT

RA~KGRnuND OF THE lNv~ UN

This invention relates to composites of cellulose based fibers dispersed in a matrix of polystyrene and to treated cellulose fibers which have improved dispersibility into polymer and improved adhesion thereto. More specifically, it relates to such reinforced thermoplastic composites which have good strength and moulding 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, such as micaplate lets or flakes. Such materials are described, for example, in U.S. Patent number 3,764,456 Woodhams issued October 9, lg73; and in U.S. Patent 4,442,243 which describes such mica-rein-forced 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 for subsequent chemical reaction with the propylene polymer wax, The use of inorganic fillers such as mica does however present certain technical difficulties. ~ica 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 of peanuts or walnuts, corn cobes, rice hulls, vegetable ~0~~

fibers and 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 for plastics. Although the use of cellulosic fillers in thermoset resins (such as the phenolics) has been as accepted practice for many years, their use in thermoplastics has been limited mainly as a result of difficulties in dispers-ing the cellulose particles in thermoplastic melts, poor adhesion (wettabili-ty) and in consequence inferior mechanical properties of the molded composi-tes.

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. Patent number 3,943,079 to Hamed described such pretreatment. Goettler in U.S. Patent number 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. Patent number 4,323,625 have shown that the composites can be produced from 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. Patent number 4,107,110 described that CC- cellulose fibers, coated with a graft copolymer comprising 1,2 - polybutadiene to which is grafted an acrylate such as butylmethacrylate could be used in reinforcing of PE and other plastic compositions.
Fujimara et al., Jap. Patent number 137,243,178 also described a cellulosic material, which has been acetylated with gaseous acetic anhydride as a reinforcing agent for polyolefins.
Gaylord, U.S. Patent number 3,485,777 (1969) describes compatibilization of polyvinylchloride or polymethylmethacrylate with grafted cellulose.
Gaylord, U.S. Patent number 3,645,939 also shows that polyethylene or polyvinylchloride or acrylic rubber can be compatibilised 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 thermoplastic polymer and cellulose.
Hse, U.S. Patent number 4,209,433 have treated wood material with polyiso-cyanate before mixing with thermosetting phenol formaldehyde resin.
Lundl et al., U.S. Patent number 4, 241,133 mixed elongated wood flakes with binder (i.e. polyisocyanate) and than hot-pressed into the form of an elongated structural member as a beam, post etc.
Wadeson, Brit. Patent number 1,585,074 describes process to manufacture cellulose-polyurethane material by reaction of fibrous cellulosics with impregnated polyisocyanates in the presence of catalyst (zinc octoate).
Nakavishi et al., Jap. Kokai 76 97648 describe the use of cellulosics in PP. Theiysohn et al., Ger. Offen 291 6657 presents heat resistant PP molding composition. Suriyama et al., Jap. Kokai 79 72247 introduces heat treated wood filler for thermoplastics. Also Dereppe et al., Ger. Offen 263 5957 as well as Kishikawa et al., Jap. Kokai 73 45540 describe filler reinforced polypropylene.

In summary, we believe to be first one to prepare composites of polystyrene and discontinuous cellulosic fibers in the presencer of small amount of isocyanate bonding agent. These composites are having good strength~ molding characteristic and are derived from readily available cheap components.

SUMMARY OF THE INVENTION

It has now been found that the cellulosic fibers can be well compatibilize with a matrix formed by polystyrene and the adhesion of cellulosic fibers to a matrix can be substantially improved when the wood fibers are chemically attached (grafted~ to a polymer compatible with polystyrene.

According to present invention, composites are made of discontinuous cellulosic fibers dispersed in a polystyrene matrix which include a bonding agent which is linear polymethylene polyphenylisocyanate (PMPPIC) of the formula:
ll~,c~
~C~
C tt2 ~ G

Composites cont~ining from 1 to 50% of cellulosic fibers by weight, based 25on the total weight of composites, are within the scope of invention. The PMPPIC is forming a strong adhesive (chemical~ bond with wood fibers (being grafted) and thus provide the composite which has improved strength and stiffness.
The bonding agent has been found to be effective at relatively low concen-35trations - as low as 0.1 parts by weight on 100 parts of the polystyrene in the matrix.
The present invention includes also the following bonding agents:

- 2?4 toluene diisocyanate which may be present also in its trimer form, - 1,6 hexamethylene diisocyanate, NCO-(CH~)6-NCO
DETAILED DESCRIPTION OF THE lNV~hllON

The cellulosic material used in the invention include cellulosic fibersderived from softwood or/and hardwood pulps e.g. chemical or mechanical or 55chemi-mechanical or high-yield or ultra-high yield or thermo-mechanical or refiner or stone groundwood or chemi-thermomechanical pulp or explosion pulp;
nut shells, corn cobs, rice hulls, vegetable fibres, certain bamboo-type reeds, grasses, bagasse, cotton, rayon (regenerated cellulose), sawdust, wood ~ 1 334558 shavings and the like. Preferred are wood fibers derived from wood pulp, e.g.
chemithermomechanical aspen pulp or thermo-mechanical pulp or sawdust. There are many available types of wood pulp which may be classified according to whether they were derived by chemical or mechanical treatment or combination of both one, as well know in the pulp and paper industry. Waste pulp and recycled paper pulp can also be used. The fibers have an aspect ratio (length divided by diameter) ranging from 2 to 5 for mechanical pulps as well as for sawdust wood flour and 15-50 for chemi-mechanical and chemi-thermomechanical pulps and 50 to 150 for low yield chemical pulps. In some instances, it is desirable to use mixtures of fibers having widely differing aspect ratios.
The polymer contained in the matrix is described as being "polystyrene" and includes both polystyrene polymer and copolymer of a major proportion of polystyrene with minor proportion of other vinylic polymer . The polymer "polystyrene" includes polystyrene of different densities as well as different proportion of crystalline and amorphous fractions.
The cellulosic based fibers are described as "discontinuous" to distinguish from the well known incorportion 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 (grafting~ agent of the invention is linear polymethylene polyphenylisocyanate of the formula:

~CO ~cG ~NCo ~ 7 ~, \,~ \,~

~ 'Y~

~__ 7 identified as PMPPIC. The PMPPIC can be of low, medium or high viscosity depending on degree of polymerization, and can be in analytical as well as technical grade. The technical grade can be formed by mixture of major proportion of PMPPIC with a minor proportion of other isocyanate e.g. 4,4' -diphenylmethane diisocyanate andlor of an adduct of the formula:

where R is ~C~ - ~~~ ~C= ~--~~~C~

C ~ ~ 2 The bonding agent can be also in form of a cyclic polymer of toluene diisocyanate. The preferred form of the bonding agent is the isocyanurate trimer represented by structural formula:

~C,O

N CO IP , ~, c ~ 3 , C ~

"C~
~ I
I ~( ~1/
Cf~

The bonding agent is used in the composites of the invention in sufficient amount to achieve an adhesive bond between the polystyrene and the cellulosic based fibers. This amount can be as little as 0.1% by weight of polystyrene, up to 10% by weight or more, on the same basis. The amount of bonding agent required can also be expected to vary with the amount of cellulosic based fiber present.
The precise mechanism of the bonding is not known, however, it is highly probable that the active isocyanate moities in the bonding agent react with the hydroxyl groups on the cellulosic base fibers, forming a chemical bond by reaction well known in polyurethane industry which is as follows:

- NC0 + H0 - ~ - N - C - O -The bonding agent can be used either as it is or in solution in a conve-nient, compatible, non-reactive solvent in order to facilitate dispersion of the active material throughout the composites.
The bonding agent can be incorporated into the composites of the invention by mixing the bonding agent therewith, before or at the same time the fibers are combined with the polystyrene, and other ingredients. If the bonding agent is added in solvent solution, the solvent will usually be removed prior to the final shaping of the compound. In case when plasticizer solution form of bonding agent is employed, this step is unnecessary.
The bonding agent may be also at first incorporated by mixing with 5 to 15 parts by weight of polystyrene based on total polystyrene weight, than mixed with cellulosic fibers on roll mill; the precoated cellulosic fiber may be than re-mixed with the rest of polymeric matrix. The bonding agent may be incorporated totaly in the pre-mixing stage or it can be also added to rP~inin~ polymer before fiber addition.
Eventhough the used bonding agent was designed for use with nylon or polyester textile it is very effective in adhering discontinuous wood fibers 6 to a polystyrene polymer matrix, the level of bonding agent~s) will normally range from about 0.5 parts up to 15 parts or more of bonding agent(s~ by ~ g weight per 100 parts by weight of fiber. In most instances, it will be more convenient to dispersed all of the bonding agent in the polymer matrix, since 5 no further additions of this ingredient need be added in making the final composit. In any case, however, the bonding agent of the present invention lO must be present in the recommended amount in order to achieve good adhesive bonding between the fibers and the matrix.

Fibers, are mixed with polymer matrix to form a composite usually in an 15 internal mixer, extruder or on a roll mill. Additional ingredients, such as fillers, plasticizers, stabilizers, colorant etc. can also be added at this 20 point.
In general, the temperatures used in roll-mill are 10 to 15C higher than that used in the extruder. The proportions of the ingredients are dictated by 2 5 the resulting composite properties.
The following specific examples illustrate the use of PMPPIC or others 30 coupling agents for cellulosic fibres.

EXAMPLE I

The wood pulp, chemithermo-mechanical aspen pulp, having properties as 40 described in Table 1, was pre-dried in a circulating air oven for 12 hours at65C. At first, zero to five weight precent of polymethylene polyphenyl-isocyanate (PMPPIC) based on polymer weight were pre-mixed with polystyrene at 45 room temperature followed by mixing on roll mill with different weight percentages (10,20,30~40~ of wood fibers.

The mixing temperatures used were 175C but could vary from 145 to 225C.
The extruded composite was allowed to cool down to room temperature and ground to mesh size 20.
5 5 The polymer-fiber mixture as prepared above was compression molded into the shoulder type test specimens at molding temperature usually 175C but could also vary from 150 to 190C, molding time 25 minutes and pressure 2.7 MPa.
The cooling time was 15 minutes at pressure of 0.5 MPa. The tensile proper-~ 1 334558 lo ties of the composites were evaluated on Instron tester (Model 4201) using the Instron A 479-521 Plastic Tensile Test Program. The reported properties are 5 those measured either at maximum values or at a break as indicated in Tables.
The reported modulus is elastic modulus defined measured at the elongation 10 0.1%.
Tensile data are presented in Table 2 and Table 3. The polymer used in this example is polystyrene identified by trade mark "STYRON-667" of Dow 15 Chemicals of Canada. The bonding agent used was polymethylene polyphenyliso-cyanate (PMPPIC) at 2 weight percents based on polystyrene used.
Tensile properties of cellulosic composites, treated with PMPPIC arecompared to that of virgin polystyrene as well as to that filled with fibers without the use of PMPPIC. It is obvious, taht presence of cellulosic fibers 25 bonded by PMPPIC led to improved adhesion and increased stress values from 34.2 MPa to 45 MPa in case of 30 weight percent of fiber addition. In the same time, the modulus has increased from 1588 MPa to 2142 MPa. In addition, energy has increased from 42 x 10-3 J to 82 x 10-3 J and elongation has improved from 2.6% to 3.5%. The values, measured at break has shown the same 3 5 general trend, being slightly lower.

TYPICAL PROPERTIES
OF CHEMITHERMOMECHANICAL ASPEN PULP (CTMP-ASPEN~

Drainage index (CSF}, ml 119 Brightness, Elrepho (%) 60.9 Opacity, (%~ 91.4 Breaking length, km4.46 Elongation, (%~ 1.79 Tear index, mN.m2/g7.2 Burst index, kPa,m2/g2.51 Yield (%) 92.0 Kappa index No 121.7 Lignin (%~ 17.9 EXAMPLE II

The composite were prepared and evaluated as described in Example I but polystyrene used at this time was the one identified by the trade mark "STYRON
- 685-D" of Dow Chemicals of Canada. The tensile results measured at break and that measured at maximum are presented in Table 4 and Table S. It is obvious that the presence of cellulosic fiber and PMPPIC lead to increase of stress values from 39.7 MPa to 49.3 MPa and modulus from 1517 MPa to 2099 MPa.
There has been some decrease in elongation as well as energy at break when compared to virgin polystyrene, but this decrease was considerably lower than that without PMPPIC being present.

EXAMPLE III

The composites were prepared and evaluated as described in Example I, but CTMP Aspen pulp was substituted by Aspen sawdust, Mesh 20 or Mesh 60. Tensile properties are presented in Table 6.

EXAMPLE IV

The composites were prepared and evaluated as described in Example I but CTMP Aspen pulp was substituted with spruce sawdust, Mesh 20 or Mesh 60.
Tensile properties are presented in Table 7.

EXAMPLE V

The composites were prepared and evaluated as described in Example I, but CTMP Aspen pulp was substituted by spruce sawdust, Mesh 20 or Mesh 60 and PMPPIC was substituted with toluene 2,4 diisocyanate. Tensile results are presented in Table 8.

EXAMPLL VI

The composites were prepared and evaluated as described in ~xample V, but toluene 2,4 diisocyanate was substituted with 1-6 hexamethylene diisocyanate (Table 8~.

Although the foregoing invention has been described in some details by the way of illustration and example for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.

~ABL~ 2 (M~ASURFU AT MAX. ) CnMPO~ItE FORC~ (N) Stl~SS (MPa.) M(!UUEUS~ (MPc~ ONGATItlN (X) EN~RGY (Jx1(1`1) Xll~r~l tO ZIJ 30 ~10 10 70 30 /10 10 70 ' 30 /10 10 ~0 30 110 10 20 30 ~10 P()l~ysryl~rNe 179 ~ 3'~.2 -~ - l5nn ~ - Z.6 ~ /12.
'-ST'~R01' -667 Po~rs~
t CTMp-AsprN 179 1131 190 19535.6 37.~1 38.2 39.2 1729 Inl3 205~ 23~11 2.5 2.7 2.3 2.3 43.1 47.3 42 '1'1 ~n ~n POLySt~'Rl.NF
~ Zl'. PMPPIC 16n 209 229Z15 35 4n.l 4.'~ 42 J7'13 In75 2142 2072 Z.5 3.1 3.5 2.9 '11 67 82 62 t Ct~1p-AspEN

~Morl~ s ~lt 0. t~ of elon~tio--FA131.1 (MEAqllll.ll Al IlRrAK~

crlMl~(lsll[ EOI~C~ (N) STRESS (Ml!a) M011ULI)SA tMP~) ELONGnTlnN (X) EN~IlGY (Jx103j %1l3Fn In 20 3n ~In 10 20 3(! ~10 10 Z0 30 ~n tn 2n 30 /In 10 zn 30 ~In rrll ys7yR~Nr slyRorl-hfi7 179 ---___ _ ___ 34.2 - ~ - '15n~3 ~ 2.6 ---~ _- 42.4 ----rn~Ysl YI~CNF
179.~1 1713.5 190 195 35.5 37.3 3n.15 39.1 1729 lnln 2052 73'11 2.5 Z.. 9 2.3 2.3 42.5 50.5 41 4tl I ~tMr-ASPCN
~n rn~ Ysl YnrN~
2~ rMrrlG Ihn 20n ZZ9 Zlr~ 3~ 3 ~In.l ~15 ~IO.Z 1743 In75 Z14Z 207Z Z.5 3.1 3.5 Z.9 ~IO.Z 6~1 79 61 CTMI'-/ISPCN

~MndullJs at 0.1~ ~r elong~tion - : -Tn~l r 4 (Mcl~sUI~rn A'r llnEAK) 051 Ir FORCr (N) S~f~SS (MP~) Mon~ s~ ONG~TION (%) ENCRGY (Jx11)3) rll~rR 10 20 3n ~n In 2n 30 ~n In 70 ln ~o 10 Z0 30 ~0 Jo 2n 30 ~n 1101 YSIYR~N~
~ Z15 ~ g.7 ~ 1517 - - - 3.n - - 79.7 .sl-YI~nN-hnsn ' r~Y5Tyl~c~ Ig3 17n 2nl 175 39 37.1 3n.7 31 lfiso 1706 192n 1993 3.1 2.6 Z.~ 2.n 5Z.641.fi 44.n 32.5 I CT~lP-l~SrCN
~n a~

rnl Y5lYnrNc 2z rMrrlc Zoo 229 2~6 207 ~o ~. ~7 ~9.3 42 16~ ls~f~ 2099 2nss 3.2 3.4 3.Z 2.6 59.6 76 75.1 ~n ctMP-nsrcN

Mnd~ s i~ t 0 .1 ~ ~ r e l nng-~ l: i nrl TAIILE S
(MEASIIRFD AT MAX. ) COMI~OSITE EnnCE (N) 51RE~S (MPa) M(lljULlJ5* (Ml'.l) tlnNGAll()N (S) ENEPGY (Jx103) Flr~r-r~ 10 2U 30 ~10 10 ZO 30 ~10 10 20 30 ~10 10 20 3n ~10 10 ZO 30 ~10 POl.YSTYREN~
21~3 ~ 10.3 ~ 1517 ~-- 3.5 -~ ----- 67.5 -----s l Yl~oN-685 D

polyslynE~lE 193.3 178 2~1 175 39.1' 37.1 3n.1 32.~ 1650 1706 1920 1993 3.0 2.6 2.~1 2.0 56.6 42.4 45.8 32.5 _~, C1'MP-/~SPEN
~0 POI YSTYRENE
Z~ PMPPIC 200 229.3 246 208 40.146.9 49.3 42 1644 1947 2ng9 2099 3.Z 3.4 3.2 2.6 61.2 77.8 77.1 4rs 6~MP-ASPEN

~Modu1us at 0.1~ of elongatlon (ME/\SllRtn AT MnX. ) COMrO~SlTlON STRCSS (Mr~) ElONGATlnN (~) ENERGY ~1)xl()~ MOllllllJS (MP~) x,nErp 10 ZO 301~ ~n 3Q 10ZO 30 In 20 30 POEY5TYRtN~- ST-YRON 667 3,~ z _ 2.59 ~ - 4Z.9 _ ~ 15nn (2~)M) 29.7 31.5 30.h 1.9n 2.04 1.7n27.5 30.t 2~1.1 l~lOZ In7fi Z051 rs ~ ASPE~3 SAIIDIISI 34 n 31.Z 17.9 Z.67 Z.09 I.rl38.9 31.~ Z9.1i 180Z IA~I9 Z131 PS 1 0.5% PMPrlC
35.5 36.n 3~.3 2.37 Z.Z~I 2.0J137.737.Z 31.0In/10 1932 1994 ,_ -~ ASPEN SAWDllST
(ZOM) PS ~ n.sx rMPPIC cx~
36.fi 36.n 3n.0 2.26 2.061.91 ~0.5 3n.Z3n.5 Inl2 ZOSO Z237 J- ASPEN SAWDllST ~
(fin~) PS ~ Z~ rMrPlC 3Z.5 35.n 3 .n l.n 1.9 1.9 25.5 31.5 37.5_330 1!~69 2Z07 ASrEN SAWVIIST
(20M) PS 1- 2~ rMPPlC 3G.5 39.2 ~n.z 2.1 2.1 1.953n.2 '11.5 39.nIn97 2072 2Z~7 1- ASrEN SAWnllST ---~
(60M) rAnl E 7 (MEASlJlltl) AT Mr~X. ) MECIIANICAI PROrEQTItS OF PS-G67 - SPRtJCt SAWUIJSl GOMPOSlTtS /IT MAXIMUM

CûMPOSlTlON STRCSS (MP~) ELONal\TlON (Xj ENERGY (J~xlO~ MonllLus (MPa) rlolC 10 ?0 JO 10 20 Jn In 7n ln In 20 JO

PoLrsTrn~N~S~lyRoN 667-- ~ 3ll-2 ~ 2-59 ~ 2-~ 15nn -PS ' SPRlJCtj SAWI)UST 31.n 3/l.2 35.32.3n 2.05 2.0i 37.7 31.7 11.7 173fi l976 2164 rs ~ SPRUCF; SAWDIJST 3~ 37 ~ 3,~ ~3 2.3~l 2.53 Z.07 39.4 44.2 3~ I727 I81t 1922 PS 1 û.5X PMPPIC
-~ SPRUCE SAWI)115T 3G.G 3n.7 37.n7.1n 2.12 1.531 3h.2 3'B.2 30.7 In61 195n 2217 ( 20M ) -~"

PS ~ 0.5X rMrPlC '~
3~.q 3n.~l 40.32.l0 2.16 2.03 37.9 42.0 ~11.3 1~n SrllllCt SAWD(IST
~60M) ps ~ 2~ PMPPIG
I SPRllCE SAI~DtJST 3~.6 39.1; 41.02.0~1 Z.05 2.06 33.9 37.6 40.3 Insl ZO3s3 2292 (20M) rs 1 2X rMPPlC
SPRIICE SAWDUST 35 3 37. l 41~nl~9~ 2.00 2.07 34.4 37 7 14.9 In7n l996 Z107 (I;OM) TAnL E R
(ME~SIIRI D AT MAX. ) MEcllANlr~Al l'Rt)PERTlES o~'r5-66r SPRUCE 5nWDllSt GOMI'()SITES Al MAXIMUM

C()MPOSlTlnN S~RFSS fMPa) El ONf1ArlON (X) ENERGY (J)xlO' MOI)III IJS (MPa) r- ltlER 10 20 3n 10 ZO 30 10 70 30 ln ~o 30 rolYsTYRENE S~YRON 667 ~ - 3~ 2 - 59 ------- - ~~ 12.~ 15138 -- - - -PS ~ SPRUCF SAWDUST 3~ ~3 3~ 7 35 3 2.3~ 2.05 2.f)1 37.7 31.7 31.7 173fi 1976 ZIG~

(-,OM) 3~.~ 31.3 3~.0 2.3~ 2.53 2.07 39.~ ~4.2 3~.~ 1722 Inll 1922 PS I 2~ DIG 35.2 3n.1 38.3 2.0 2.1 1.9 3t.5 37.3 3~.3 ll333 1978 2031 - SPRIICE SAWnUST - ~n (20M ) PS + 2~ OJIC 36.n 35.5 39.1 2.2 1.9 1.9 39.n 32.5 37.3 1756 195~ 2209 SrRllCE SnWDUST
(60M ) PS ~ 2~ IIMD I C
RlJCE ~WOI~ST 32.233.2 32.~3 I.n 1.7 1.5 26.5 25.0 22.n _767 ~863 2_~2 (20M) PS ~ 2~ IIMDIC
I~E AW 3'i.331.9 36.3 2.0 1.7 1.7 33.2 26.7 29.5 1761 1906 2160 SPRl ~ S DllST - - - - ------- -- - -- _ _ ___ (60M) Tl)IC.... Tolllene di~socy;llla~
IlMr~lC.... hexamethylenedii~onyanale :~ `

Claims (10)

1. A composite comprising discontinuous wood cellulose fibers dispersed in a polystyrene matrix, the fibers and polystyrene being bonded to each other by 0.1 to 10% by weight based on the total composition of linear polymethylene polyphenylisocyanate or 1,6-hexamethylene di-isocyanate or toluene 2,4 di-isocyanate, the composites further including up to 50% by weight (based on the total composite) of plasticizer and up to 40 % by weight (based on the total composite) of inorganic filler.

2. A composite according to Claim 1 wherein the fibers are pretreated by precoating with polystyrene.

3. A composite according to Claim 2 wherein fiber material of the precoated fibers is 1 to 50% by weight of the total composite.

4. A composite according to Claim 1, Claim 2 or Claim 3 wherein the cellulosic fibers are from hardwood or softwood pulps or their mixtures.

5. A composite according to Claim 1, Claim 2 or Claim 3 wherein the cellulosic fibers are from wood flour, sawdust or shavings or their mixtures.

6. A composite according to Claim 1 wherein the fibers have a fiber aspect ratio from 2 to 150.

7. A composite according to Claim 1 wherein an inorganic filler material is present and is mica, talc, calcium carbonate, silica, glass fibers, asbestos or wollastonite.

8. A composite according the Claim 1 wherein the cellulosic fibers are 40%
by weight of the composite and the bonding agent is present at 7.5% by weight based on the cellulosic fibers.

9. A treated discontinuous wood cellulosic fiber treated with polystyrene containing 0.5 to 15% by weight, based on the fiber, of 1,6-hexamethylene di-isocyanate or linear polymethylene polyphenylisocya-nate or toluene 2,4 di-isocyanate.

10. A compression or an injection molding made from a composite of Claim 1.