CA2050600A1

CA2050600A1 - Cellulosic product, process for the production thereof and uses thereof

Info

Publication number: CA2050600A1
Application number: CA 2050600
Authority: CA
Inventors: Andrew B. Hayns
Original assignee: Individual
Current assignee: FOSSE Ltd
Priority date: 1989-03-31
Filing date: 1990-03-30
Publication date: 1990-10-01
Also published as: EP0466760A1; AU5400690A; JPH04506191A; WO1990011978A1

Abstract

2050600 9011978 PCTABScor01 Cellulosic pulp material is dewatered and/or dried to a water content of up to 20 % by weight. With its dry matter content of up to 55 % by weight of cellulosic fibres and not less than 45 % by weight of inorganic filler particles, the product obtained finds use as such as an extender in horticultural products, as cat litter, inter alia, and, if sufficiently dry and mixed with a binder forms a moulding composition from which shaped products having useful properties and which may be biodegradable are obtainable.

Description

WO90/11978 pcT~GB9o/oo47~

2~5~

CELLULOSIC PRODUCT, PRO OESS FOR T~E P~ODUCTION THE~EOF
AND USES THEREOF
This invention relates to a cellulosic product, process-for the productlon thereof and uses thereof.
~he invention has particular application to the processing of waste from paper m~lls.
In the Unlted Kingdom alone, over 500,000 tonnes of waste are produced annually from paper mills. The wast2 is approximately 70% water an~ 30~ dry matter by weight; the latter is made up of approximately equal proportions of clay (from the mlneral filler u~ed in paper ~aking) and cellulose fi~res.
Although large quantities of this waste have been generated for many years, a satlsfactory means of utllising the material has not hitherto been available.
Paper makers c~rrently bear the cost of disposin~ of the material.
8P-B-0 039 522 discloses a process for ths manufact~re of l~quid and shock absorbing mater~al from a suspens$on consisting wholly or substantial~y of cellulose fibres. The suspension iq waste from a manufactur~ng process in which fibres consisting wholly or su~stan~ially of cellulose material are processed by a wet method. The dry matter content of the waste is required to contain 60-80% by weight of cellulose fibres, from 20-40% by welght of inorganic filler and from 0-10% of an adm~xture which is incorporated to modlfy the properties of the end product (pellets).
The proce3s involves dewater~ng the initial suspen~ion to a water content in the rang~ of 40-80% by welght and then pelletlsing th~ 8emi-dry masS by squeezing it through one or more narrow apertures. The resultant pellets undergo a drying process. The pelletising and drying conditions are ad~usted so that the end product has a bulk density of 150-400 kg/m3 and a water content of 0.5-l0~ by weight. The initial dewatering step is WO ~/11978 PCT/GBgO/ ~ 75 20~0~

preferably such as to give a semi-dry mass containing 55-65% by weight water.
The need to use a starting material consisting substantially of cellulose fibres limits the applicability of the process disclosed in EP-B-0 039 522 in that the bulk of the waste material produced from paper making is unsuitable by virtue of its high clay (filler) content.
It is an ob~ect of this invention to find a use for waste material as such produced from paper making.
According to one aspect of this invention, there is prov~ded a material in block or sheet form or ln free-flowing particulate form which is a dewatered or dried cellulosic pulp material having a water content lS in the range of up to 20% by weight and whose dry matter content comprises up to SS% by weight of cellulosic fibres and not less than 45% by weight of - inorganic filler particles.
In a second aspect, this inventton provides a pr~cess for the production of a material accord~ng to the first aspect of this invention, which process comprises dewatering an aqueous slurry or sludge ~ containing cellulose fibres and inorganic filler, the -~ resulting product having a dry matter content which 25 ~ comprises up to 55% by weight of cellulosic fibres and not less than 45% by weight of inorg~n~c filler particles and drying the resulting product to a ~- residual water content of up to 20% by weight, which dried product is recovered in block, sheet or free-" ~
flowing particulate form.
When the drled product i8 to bo recovered in particulate form, a pelletising Qtep may be caried out before or even after the drying step. Alternative~y a dry product in the form of a sheet or block may be comminuted to form a free-flowing meal. A dried product containing above 10% by weight water content is ,:

WO ~/11978 ~ /~ 75 typically grey in colour and has the texture of cotton wool. Hence it may be termed ~flock"~ 5uch dried product preferably has a moisture content in the range from lO to 15~ by weight. A product with such moisture content, even if only in sheet or block form can be used, with the minimum of breaking up, as an extender, for example in horticultural products, typically in peat-based products.
For many uses, however, the dried product 18 -pelletised or otherwise comminuted, as will be described hereinafter.
The dewatering step is advantageously carried out on a sludge containing cellulose and inorganic filler usin~ a filter press, preferably a screw press. Such sludge is generally to be obtained by flocculation of the slurry obtained in paper production. The final water content of the mass resulting from the dewatering stage is preferably 45-50% by weight. We have found that the "Perrin~ Pusher Screw Press manufactured by Wlll~am R. Perrin, Inc., 432 Monarch Avenue, AJax, Ontario, Canada LlS 2G7 works well in the process of this invention.
Unlike the process disclosed in EP-B-O 039 522, the present invention may have a drying step preceding a comminuting step. When drying precedes comminuting or in the more specific case pelletising, the surprising result i8 obtained that starting materials containing higher proportions of mineral filler are amenable to processingl and give useful end products.
~hs aforemQntioned drying step carrled out after dewatQri~g is preferably a flash drying step.
Advantageously, the drylng step is carried out in an apparatus which simultaneously pulverlses and dries . further the dewatered feed mass of flock material.
Apparatus suitable for this purpose is manufactured by Atritor Lim~ted, P.O. 80x lOl, Coventry CV6 5RD, WO90/~1978 PCT/GB90/ ~ 75 2 ~ 3 England. The process of this invention is not limited however to the use of this particular apparatus or to any specific means for subdividing the flock.
Alternatively, when lower residual moisture contents are required, in particular in the range of 0.25 to 1% by weight for reasons which will become apparent hereinafter, drying, with or without use of an intermediate flash drying step, is advantageously carrled out on a vibrating fluidizing bed or on a rotary louvered dryer.
After the dewatering step, selected additlves may be incorporated into the semi-dry mass prior to lts entry into the drying phase. Typical additives (which will be selected according to the intended end use of the final product) are colorants, fertilisers, odourants and absorbent.
When pelletising as such is carried out in the process of the present invention, it is preferably carried out using an animal feed pelleting mill or an equlvalent mill, so as to produce pellets which, if desired, may then be compressed. The product obtained ln this way is useful as cat litter or as hygenic bedding for the broiler industry.
Suitably divided very dry material (generally 0.25 to 1% by weight water content) has been found to have additional important uses. By for example incorporating a resin into the material fed to the drying stage, a final product can be obtalned which is suitabl~ for shaping. iThis resin may be biodegradable and may be starch derived. In any Ca8Q it will generally be pre8en:t only in minor ~mount. A product can thus be obtained which is suitable for example for shaping lnto plant pots which because of thelr constitution can be set in earth as such with a plant therein, there is no need to remove the pot and discard it when planting.

wo9o/lls78 PCT/GB90/ ~ 75 -5- 2~ 0~ 1 Thus, according to a third aspect of the invention, there is pro~ided a moulding composition comprising an intimate mixture comprising (a) dried or dewatered cellulosic pulp having a dry matter aontent of up to 60% by weight cellulose fibres and at least 40% by weight inorganic filler and containing little or no water, and (b) a binder, the binder constituting at least 2% by weight of the composltlon.
The binder ls preferably a synthetlc resin. For many products, it will be sufficient to use scrap polymer as binder. If the proportlon of pulp residue present in the matertal with which the binder ls blended is high (50% or more by weight) the polymer should be in finely divided form. The binder is ~5 advantageously present in an amount of at least 5% by weight of the composit~on. For many applications, a binder content in the range from 10-60% by weight will be acceptable. Preferred binder contents are in the range 10-30% by weight; moulding compositions of the invention having a binder content ln this range are exc~ptional in that they are suitable for in~ect~on ~oulding, despite the very high filler content.
Both~thermoplastic and thermosetting resins may be u~ed as synthetic resin binder.
- 2S The presently preferred thermoplastic resin binder materials are for example low density polyethylene (LDPE), polypropylene (PP), ethylene-propylene copolymer3, acrylonitrlle-butadiene-styrene copolymers, poly~mldes, especiallyinylon, ln particular nylon-6, and thermoplastlc rubbers. LDPE and PP are preferred bscause of meltlng rang .
Thermosetting reslns whlch may be employed include urea/formaldehyde, phenolic, polyurethane, polyisocyanurate, polyurea, polyester, epoxy and bismaleimlde resins as well as polyamide caæting systems, e.g. Nyrim ~Registered Trade Mark). The ~WO90/llg78 PCT/GBgO/~7s -6- 2 Q ~ f~
resin forming material in general may be fixed with the cellulose-containing material either before drying or after drying thereof to a suitable state for moulding.
The character of the thermosetting system to be S employed will determine the stage at which mixing wi~h cellulose-containing material which is to be dried, is being dried or has been dried is to occur and the material to be then mixed with such material. Some systems will generally require a peroxide or other catalyst and the character of the system will depend upan how it is constituted. Thus, when unsaturated polymers or cross-linkable monomers aré to be cured in situ using a peroxide or other catalyst, for example when using unsaturated polyesters, acrylics and allyl - 15 resirs, it is necessary to consider two-pack systems with catalyst only being introduced prior to the moulding stage. Where catalysts are only activated at high temperatures, for example above 150C, a "two-pack" approach is not required. Such situation applies to such general thermosetting ma~eriAls as phenolic resins, urea-formaldehyde resins, melamine-formaldehyde resins, polyester sheet moulding compounds (SMC) and d~ugh mQulding compounds (DMC).
The mixing of additives into a composition containing large guantities of pulp residue will generally require a dough mixer or planetary mixer owing to the viscosities involved. The high viscositles resulting from the presence of large quantities of~pulp r~sidue (i.e.~ more than 30%) in the composltion~ will al80 prevent the proces81ng of these composltlons by tradltional casting techniques. Should relatively high pressures be necessary to ensure adequate filling of moulds, compression moulding is therefore a suitable technique to adopt.
Alternatively, in~ection moulding may be feasible, although its use will be limited to lower melting ~0 ~/11978 PCT~GB~/~7~
2 ~

polymer-containing moulding compositions as too high a temperature will induce degradation of the cellulose.
A preferred moulding eomposition aeeording to a fourth aspect of the invention is an in~eetion moulding composition whieh eomprises an intimate mixture derived from (a) dried or dewatered pulp obtained as a waste produet from a paper making proeess, the pulp eontaining, as dry material, up to 60% by wel~ht eellulose fibres and not less than 40% by weight inorganie filler and eontaining llttle or no water; and (b) a thermoplastie resin, e.g. low density polyethylene, the resln eonstltutlng at least 5% by weight of the eomposition.
Compression mouldlng of eompositlons embodylng the invention works satisfaetorily over a wide range of binder eontents in the eomposition. It is possible to form artieles from preferred eompositions in aeeordanee with the invention by in~eetion moulding even at relatively low blnd r eontents. In~eetlon mouldlng of m~t rlals eonvention~liy requires a eonslderable proportion of binder to he present in order for the in~eetion moulding to work satlsfaetorlly. We have ; found that sueeessful in~eetion moulding runs ean be aehieved with eompositions of this inventlon wlth a .~ 25 binder eontent (speeifieally, but not neeessarily only wlth low d~ensity polyathylene) as low as 5~ by weight of this eomposition and gen~rally as low as 10~ by weight.
Ifideslred,~one or more addltlves may be ineorporated into a mouldlng eomposltlon ln aeeordanee wit~ th$s lnvention, typie~lly in relatively small -~ amounts, e.g. up to about lO~ by welght of the eomposltion. Sueh additives inelude fire retardants, eolorants, water repellants and other eonvention~l ingredients. Moulding eompositions embodying thls inventlon llke the aforementioned Nfloek" and similar ','~
,~

~WO90/11978 PCT/G890~7s 2 ~ ~ 5 i~ 3 material are hygroscopic and need to be bagged as soon as possible after their production. However, moulded pr~ducts produced thererom, as a result of the effect of the binder, are less hygroscopic.
For use in forming a moulding composition of this invention, the waste from paper making is preferably dried directly to a very low water content after being sub~ected to prelimlnary dewatering. ~hereafter the dried pulp can be mixed intimately with a binder, typ~cally a resin, ~o form the moulding compos~tion of this in~ention. Mlxing with binder is preferably carried out using a Z-blade mixer or a planetary mixer and/or by feeding the starting ma~erials for produc~ng the moulding composition through an extruder. More homogenous mixing can be achieved if an initial Z-blade mixing process is followed by one or two passes through an extruder, e.g. a Betol extruder. It is convenlent for the dried cellulosic pulp to be in the form of pellets or granules as it is supplied to the mixing process. Granulation of air dried pulp may ~e carsied out ln a Christy Norris Spruemaster grarlulator which can be fitted with differerlt size sieves to control crumb size. If mixing wlth binder takes place at an early stage in the drying. cellulose con~a~ning waste whose water content is still as high as 40% by weight may be contemplated. Such cellulose-contain~ng mater~al will however have a bulk which is disadvantageous; mixing o~ the flock with the binder is less qonveni~n~ than using dried granules~or p~llets.
Moreover the presence of substantial amount~ of water produces vapour problems in an extruder used for mixing and in subsequent moulding equipment.
When the compounding of pulp residue with ~inder comprises an extrusion techni~ue, compounding can be successfully carried out in a conventional twin-screw compounding extruder. For low density polyethylene, -~090/11978 PCT/GB90/00475 -9- 2~ 6a~
barrel temperatures in the region of 150-160C and die temperatures around 170C can be used. The extrudate itself can be pelletised. To obtain a completely uniform product, overall intensive mixing is required S and this may be achieved by (a) passing the extrudate through the extruder a second time or (b) fitting a cavlty transfer mixer between the barrel and the die or (c) using a specialised c~mpoundlng machine, e.g. Bus Ko-Kneader.
Polymers which have high melt temperatures may cause dlfficulties as the cellulose flbres present can degrade. For example, nylon-6 having a melting point of about 215C can only be blended with cellulose-containing material provided that the residence time of the mix in the barrel of an extruder is kept as short as possible. No problem in this respect is achieved with polypropylene which has a melting point of about Pulp residue contalning in~ection moulding cc3pos$tlons ~ould e~sily. The pulp residue appears to h~ve a lubricating effect. How~ever, when high filler ~ and fibre contents are employed (greater than 50% by -~- w d ght of pulp residue), difficulties may be - encountered in injectlon mouldlng of thin sections.
- 25 Moulding compositions containing pulp residue ~ mould more easily than compositions containing similar -; l~vels of re conventional fillers. In some e bcdi ents of the invention, one or more conventional flllers m~y b~,incorporated into a mould~ng composition accord~ng to thi8 invention. Such fillers ~nclude powders, gla8s, wood, fi~re, talc and whitlng; the ;~ inclusion of these additlonal fillers may be deleterlous lf the composltion ls to be in~ected moulded. Higher filler loadings are possible with pulp residue th~n conventional fillers such as glass fibre, whiting, china clay etc. used as sole source of filler.

--WO ~/11978 PCT/GB90/ ~ 75 -lo- 2~
Although the use of cellulosic pulp in the practice of this invention is mainly described herein with reference to utilization of paper mill waste, pulped waste paper can also be as an alternative or in addition thereto.
The following examples illustrate the invention.
In the examples, reference will be made to the accompanying drawing. The term n flock~ is used in the examples to denote feedstock containing cellulose and filler wlth wh~ch binder is mixed.

Waste from a paper mill is supplied at l to a screw press 2. The waste contained dry matter consisting, by weight of 50% inorganic filler (clay) lS and 50% cellulose fibres. The solid matter content of the waste was approximately 30% by weight. The output of the screw press (at 3) had a moisture content of about 45% by weight. This partially dewatered material was-supplied to a flash dryer 4, which was an ~Atritor dryer-pulverlser~ manufactured by Atrltor Llmited of Coventry, England. The output from dryer 4 was a grey fluffy materlal wlth a low water content. In one embodiment of the ~nvention, this material may be used ~ directly as a drying or absorbing agent or as an -~ 25 extender, e.g. for horticultural composts.
In another e bod1ment, the output at 5 from the dryer 4 i~ fed to the input 6 of the pelletising press.
~- This may be a conventional pelletising press of the type used for pelletlsihg animal feed. The pelletiqed product pa8ses (at 8) to a two-stage packing plant 9, ,~ 10.
If desired, additives may be incorporated into the feed stock at the input to the flash dryer 4.
The final, pellet$sed product may be used as cat litter, or for other applications where good liquid absorbing and/or shock-absorbing products are required.

WO 90/lV78 PCI'/GB90/00475 The product m~y also be used in the production of moulding compositions when its moisture content is reduced fur~her.

The procedure of Example 1 was modified in that using a "Perrin" Pusher Screw Press, the starting sludge was ~nitially dewatered to around 50~ dry weight. The output from the screw press was fed to a "Atritor" dryer-pulveriser which reduced the water content of the material to approx~mately 30%. The resultant grey flock product was then dried to substantially complete dryness in an oven at 110C. At the end of this process, the dry cellulosic flock contained only 0.6% by weight of water. The dry flock was then mixed in a Kenwood planetary mixer with a commercially available }ow d-ensity polyethylene (LD110 manufactured by Plascoat Systems) for three minutes.
In a first run, 124 parts by weight of the dry flock were mixed with 16 parts by weight low density polyethylene, this corresponding to 11.4% by weight resin in the composition (dry weight). The mixture obtained in the planetary mixer was then passed twice through a Betol extruder. The resultant intimate mixture was then used to form in~ection moulded pots us~ng a DAn~els Press operating at 180C. Thè
~- resulting product was easily demouldable and had a smooth uniform glossy dark grey appearance.
A second sample of the dry flock was treated in the same way asldescribed abuve, except that the mlxture supplled to the planetary mixer consisted of 138 par~s by we~ght dry flock and 40 parts by weight low density polyethylene (LDI10). This corresponds to 22.5% by weight resin in the composition ~dry weight).
As with the previous sample, injection moulding produced a satisfactory product with no processing difficulties.

. ~ WO90/11978 PCT/GB90/0047~
2~?~s9~0~

Following the procedure of Example 2, further injection moulded products containing pulp residue and low density polyethylene were produced, the contents of flock (dry weight) in the moulding produced amounting to 50, 65 and 85% by weight. For comparison, a moulding was produced from the low den ity polyethylene alone.
The properties of the products thus obtained were then invest~gated. Firstly strength and modulus values were determined and yielded the following values:-TABLE l .
Property % Flock in Compound lS

.
Flexural Strength No failure 17.116.4 10.8 Mpa Flexural M~dulus 0.24-0.33 1.31.69 2.5 GPa .
Tensile Strength 8.3-31.4 4.978.84 5.97 MPa .. . . .

As with the!flexural and tensile properties, the intensity o mixing and the moulding conditions will considerably in~luence the impact properties. In particular, the ~mpact strength w~ll be subJect to greater variability if mixing has not been int~nsive.
All the aforementioned samples were mixed under the same conditions and they were subjected to impact test measurement which yielded the following results:-~ -' 90/11978 P~/GB90/00475 ,_ -13- 2~6~

% Pulp Residue 0% 50% 65% 85%
~;
Impact KJ/m2 No break 4.4 S.4 6.5 Izod Test The moulded artlcles werQ all sub~ected to working following woodworking techniques, for example, drilling, nalling, screwing and sawing, and no problems were encountered when the pulp residue constituted 50-8S% by weight of the moulding.
The incorporation of flock enhances the fire resistance of polyethylene moulded bodies which will not;melt, drip or lose int-grity in the same manner as unmodi~fied~polyethyl~ne when pulp residues are high, e.g. 85-80~. ~owever the compogitions still burn and are~not~self extinguis=hlng.
; 20 Fu~ther tests were carried out on the d ~reaeneLoned mouldings, which~ being relatively por~cus, can absorb signif~cant amounts of water or solvents.~MouIdings containing high levels of pulp residue are most affected as shown by the following . ~
~ 25 results:-,; ~,., "~
" ~

:~:
, ,, . ,, ' :~

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,~

~'0 ~1197B PCTlGB90/ ~ 7~
.
-14- 2 ?~ g % Pulp Residue ~ by wt. of water absorbed by immersion in moulding 24 hr. 1 week 1 month 2 months _ _ _ _ 0 <0.01 NA NA NA
1.1 3.0 6.3 8.4 1.5 4.2 8.9 10.2 2.6 8.5 12.1 12.3 NA - Not available If the moulding compositions are not uniorm1y compounded, this may lead to warping. Significant dimensional changes may occur in humid environments owing to water uptake. Water may extract material from the mouldings during prolonged immersion as sugges~ed by the following results:-% pulp Residue 0 50 65 85 - in moulding 25 % extracted after~,~ O <.1 ~.1 1.
2 months immersion in water _ Comparable experiments carried out using an orgaoic solvent (petrol) showed the extent to which it may also be absorbed by pulp residue/polyethylene mouldings or extracts material from such mouldings.

WO90/11978 PCTrG890/~75 -15- 2 ? ~, 9 ~5 ;~, ~

% Pulp Residue % by wt. of petrol absorbed by immersion in moulding 48 hr. 1 week 1 month 2 months S _ 6.2 7.1 7.3 7.7 5.9 6.5 6.4 7.0 3.3 3.1 3.2 3.7 . ..

.

% Pulp Residue 0 50 65 85 15 in moulding % by wt. material ~ NA 1.9 2.6 4.8 ex~tracted in 2 cntbs 20~
, ~ ~ ~ ,. . __ In each of the following examples, there was used a~pulp rssidue from a waste paper mill which had been d wat red~and dried to a`resldual water content of less ~hAn~1% by~w d ght, the pulp re ldue having a dry weight compositiQn of 50% cellulose and 50% clay.
;~r_ ~ ' EXAMP~E -4 ~-~ 100 gr~s of dried pulp res1due were placed in the , ..
~ m~Y~ng!~cha b r~of~ a! ~mJll pl~netary mdxer followed by ;~ 30 47.5g of epoxy resin (Eplkote 828, Shell Chemicals).
~ The cur1ng~ugsnt, 2.5g of benzyl dimethylamine, W~8 y~ add-d over a 5 minute period and mixed in for a further 15 minute This was designated Compound A.
~5~ ' A portion of Compound A was pressed in a steel mould at 80C to produce sheet mould$ngs approximately ~ 1.2mm X 115mm X 115mm. A pressure of approximately ,,, ,~ ~

, . " ~ , -,i, ~:

WO90/11~8 PCT~GB90/ ~ 75 -16- 2~ a 0 900kg was applied to the mould and the moulding was removed after 15 minutes. The product was a hard, rigid sheet.
A second portion of Compound A was pressed in a different steel mould at 80/100C for 3G minutes to produce a sheet 2.7mm X ll5mm. A pressure of approximatqly 900kg was applied to the mould. The product was a hard, black, rigid sheet.
When Compound A was left overnight before use unsatisfactory mouldings were produced owing to moisture uptake.

4 grams of phthalic anhydride were dissolved in 50 gram;s of acetone and this was mixed into 45 grams pulp residue using a small planotary mixture. Then lO grams of an epoxy resin (Epikote 828 from Shell Chemicals) was mixed 1 . The mixture was spread out on a tray to -allow~most of the acetone to evaporate. This took ~approxL~ately l hour. Thi~ wa d~signated Compound B.
A~pcrtlon of Co pound B was then pressed in ll5mm X
l.2mm sheet mould for l hour at 150C. The product was ~-~ a hard r~gid black sheet.
` If Ccmpound B was left overnlght before use unsatisfactory mouldings were produced owing to moisture uptake.
.,.:

; lOOg of~;dried pulp re8idue wsre placed ln the mixlng vessel of a 8mall planetary mixer. Then a -~ premix of 20g linear polyether diol (Desmophen l900 from Bayer UK), O.Ol dibutyl t~n dilaurate ~nd 0.05g of a 33% solution of triethylene diamine in polyethylene :~.
glycol molecular weight 200 was prepared. This premix was mixed into the pulp residue for 30 minutes. Then 27.4g of polymeric diphenylmethane diisocyanate ., ~.
, . . .

,,~ .,~
~,-, ::
., WO90~11978 PCT/GB90/ ~ 75 -17- 2 0 ~ 3 (Suprasec DND from ICI) were mixed in for 20 minutes.
This was designated Compound D. The amount of isocyanate and polyether used were such that an excess of isocyanate was present.
A portion of Compound C was immediately pressed at 80/100C in a llSmm X llSmm X 1.2mm sheet mould. A
pressure read~ng of 2000psi (13790 kpa) was used for 20 minutes . The product was a tough rigid sheet.
Approximately 30 mlnutes after mixing~ a portion of Compound C was pressed at 80 to 100C in a 115mm X
llSmm X 2.7mm sheet mould. A pressure reading of 2000psi (13790 kpa) was used for 100 minutes, This product was a tough rigid sheet.
If Compound C was left overnight before use, unsatisfactory mouldings resulted.

lOOg of dried pulp residue and a pre-mix of SOg Deæmophen 1900, O.lg of a 33% solution of triethylene diamine in polyethylene glycol of molecular weight 200 and 0.03 dibutyl tin dilaurate were mixed on a planetary mixer before mixing in 7.8g Suprasec DND.
This was designated Compound D. A portio~ of Compound D was compression moulded as in Examples 4 and 5.
2S The compression moulded sheets were soft and exuded traces of unreacted polyQther d~ol. The amounts of ~socyanate and polyether used were of stoichiometric equivalent molar guantitles.
; i lOOg of dried pulp re~idue were mixed with 34g of a pra-mix of 68% Desmophen 1200 (a branched polyester polyol), 0.02g dibutyl tin dilaurate and 0.08g of a 33%
' solution of triethylene diamine in polyethylene glycol (m.w. 200). This was carried out in a planetary mixer over a 1 hour period.

WO90/11~8 PCT/GB90/00475 -18- 2~ 3~, Then 14g Suprasec DND were added and ~ixed in over 15 minutes. This was designated Compound E. The products were pressed into sheets as in Example 6.
The sheets were hard, rigid and black. An improvement had been brought about by using a more reactive polyol with a branched structure. Also, though equivalent amounts of polyester polyol and isocyanate were used, the formulation contained a higher percentage of isocyanate and was better able to tolerate trace guantities of water.

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Claims

CLAIMS:

1. A material in block or sheet form or in free-flowing particulate form which is a dewatered or dried cellulosic pulp material having a water content in the range of up to 20% by weight and whose dry matter content comprises up to 55% by weight of cellulosic fibres and not less than 45% by weight of inorganic filler particles.

2. A material as claimed in claim 1, having a water content in the range of from 10 to 1596 by weight and having the texture of cotton wool.

3. A material as claimed in claim 1, having a water content in the range from 0. 25 to 1% by weight.

4. A material as claimed in claim 2 or 3 which is in the form of pellets.

5. A material as claimed in claim 3 which is in the form of a granulate.

6. A process for the production of a material according to claim 1, 2 or 3, which comprises dewatering an aqueous slurry or sludge containing cellulose fibres and inorganic filler, the resulting product having a dry matter content which comprises up to 55% by weight of cellulosic fibres and not less than 45% by weight of inorganic filler particles, and drying the resulting product to a residual water content of up to 20% by weight, which dried product is recovered in block, sheet or free-flowing particulate form.

7. A process as claimed in claim 6, which comprises pelletising the material before or after said drying.

8. A process as claimed in claim 6 or 7, whose product is subjected to granulation.

9. A process as claimed in any one of claims 6 to 8, wherein said drying is carried out by flash drying and/or on a vibrating fluidizing bed and/or a rotary louvred dryer.

10. A process as claimed in any one of claims 6 to 9, wherein the dewatering is carried out to a water content of from 45 to 50% by weight.

11. A moulding composition comprising an intimate mixture comprising (a) dried or dewatered cellulosic pulp having a dry matter content of up to 60% by weight of cellulose fibres and at least 40% by weight inorganic filler and containing little or no water and (b) a binder, the binder constituting at least 2% by weight of the composition.

12. A moulding composition as claimed in claim 11, having a resin binder content in the range of from 10 to 60% by weight.

13. A moulding composition as claimed in claim 11 or 12, comprising a thermoplastic resin binder selected from low density polyethylene, polypropylene, ethylene-propylene copolymers, acrylonitrile-butadiene-styrene copolymers, polyamides and thermoplastic rubbers.

14. A moulding composition as claimed in claim 11 or 12, comprising a thermosetting resin or precursors thereof, selected from urea-formaldehyde, phenolic, polyurethane, polyisocyanurate, polyurea, polyester, epoxy and bismaleimide resins.

15. An injection moulding composition which comprises an intimate mixture derived from (a) dried or dewatered pulp, the pulp containing as dry material up to 60% by weight cellulose fibres and not less than 40%
by weight inorganic filler and containing little or no water; and (b) a thermoplastic resin, the resin constituting at least 5% by weight of the composition.

16. A moulding composition as claimed in claim 15, wherein the thermoplastic resin is low density polyethylene.

17. A moulding composition as claimed in claim 15 or 16, wherein the pulp is obtained as a waste product from a paper making process.

18. A process for producing a shaped product which comprises compression moulding a moulding composition as claimed in any one of claims 11 to 14.

19. A process for the production of a shaped product which comprises injection moulding a composition as claimed in any one of claims 11 and 15 to 17.