|Title of Invention||
"A NOVEL MOLDING COMPOSITION, A PROCESS FOR MAKING INDUSTRIAL PRODUCTS USING A NOVEL MOLDING COMPOSITION"
|Abstract||A novel molding composition and a process for making industrial products using the novel molding composition." A premix composition based on natural fibres have been developed. It can be used for molding small electrical components, instrument panels, gear box covers, air condition housing, roofing tiles, doors, wash basin etc. The composition comprises 30- 50 wt% unsaturated isophthalic based polyester resin, 9-15 wt% vinyl monomer blends of styrenemethyl methacrylate and styrene-n-butyl methacrylate, 8-20 wt% surface modified natural fibres such as chopped sisal, jute, coir, sunhemp, 3-8 wt% chopped glass fibres, 30 - 45 wt% surface modified wollastonite of aspect ratio (1/d) 20 -30 , 1 - 5 wt% zinc oxide, 0.5 - 3 wt% calcium stearate, 0.5 - 1.5 wt% benzoyl peroxide and 0.5 - 1.5 wt% cobalt naphthenate.|
|Full Text||The present invention relates to a novel molding composition, a process for making industrial products using .the said composition and industrial products made thereby.
Interest on developing new materials alternatives to metal, concrete etc. has increased widely in recent years. One of the
strong option to develop substitute materials is thecomposites
based on natural fibres. The development of chemically modified natural fibres has made the material worthy of consideration both on its own and as a supplement to more traditional reinforcements. Keeping this in view, premix formulations based on natural fibres have been developed. It can be used for moulding small electrical components, instrument panels, gear box covers, air conditioner housings, roofing tiles, doors, wash basins etc.
Dough molding compounds (premix) are becoming more widely used because of their lower relative cost, good moldability, high corrosion resistance and better stability. Catalysed unsaturated polyester resin, mineral filler and chopped glass strands (lengths 1/4-1/2 inch or more) are blended in a suitable compounding machine, resulting into a paste like material suitably termed "dough molding compound" by the British but known better as "premix". Because dough molding compound flow readily, they may be moulded by compression, transfer or injection and the pressure required to produce a component is relatively low so that large moldings can be produced without much difficulty. The initial use of dough molding compound was restricted to unstressed or minimally stressed components. Investigations on
the mechanical properties of dough molding compound have provided information on the behaviour of a complex material and the effect of constituent phases. The material can be considered to be linear-elastic for strains upto approximately 0.2 % (Ogorkiewicz, R.M., "Stiffness and strength of polyester dough molding compounds", Composites, 4, No 4, 1973, p. 162). Much of the increase in stiffness in tension, shear and bending is due to the addition of filler to the molding resin, when the only addition to the resin is filler, there is no improvement in compressive strength and the strength in bending is reduced (Ogorkiewicz, R.M. and Mucci, P.E.R., "Influence of fillers on the stiffness and strength of a polyester resin", J. Mater. Sci. 10, No. 3, 1975, p. 209 ) . Attempts to predict the tensile strength, work of fracture and fracture toughness of dough molding compound were made using theory for idealized composites but the results are unsatisfactory (Harris, B. and Cawthorne, D., "The strength and toughness of dough molding compounds", Plast. and Polymers, 42, No 161, 1974, p. 25) . Fracture energy and fracture toughness were found to be dependent on the glass content. To explain the mechanism of failure at elevated temperatures, fracture energy measurements have been correlated with dynamic storage and loss shear moduli; the glass transition temperatures of the matrix resin and that of the fibre-matrix interface were found to be important in predicting the failure behaviour.The response of polyester molding compounds to cycle tensile loading has been further reported as a function of number of reversals. When the cycle load is above the knee point, the behaviour of dough molding compound resembles that of ordinary
glass fibre reinforced plastics but below this level, dough molding compound appear-to be rather less sensitive (Harris, B. et al. , "Cyclic loading and the strength of dough molding compounds", Composites, 1977, p. 185). In another study, results indicate that the scatter in fatigue life was found to be greater than that the reported for other reinforced plastics. No significant difference in the scatter of fatigue lives was observed between groups of specimens taken from a given sheet or selected at random from different sheets ( Rose, R.G. and Huston,R.J.,"Tensile and fatigue properties of dough molding compound", Composites, 1978, p. 199). Assessing fully the properties of dough molding compound, molded roof tiles have been prepared using 15-21 wt.% unsaturated polyester resin and 3-12 wt.% chopped glass fibres with the balance of the compound mainly mineral coarse (25- 1000 ^im) and fine particles (25 aim) (Fry,D.P.,"Dough molding compounds for producing building materials", Pat .G B _2196 .344 _A, 1988, UK). Dough molding compound formulation was further maximised to obtain good flame retardancy and improved impact strength properties for making typical automotive components. Attention was also given on designing of injection mould to minimise fibre damage and orientation (Whelam,T.; Goff,J.,"Dough molding compound-material properties", XXIII, Br. Plast. Rubber, 1986, p. 79). Molding compounds having a long shelf life were formulated using unsaturated polyester resin, monomers, conventional additives and an inhibitor combination. The inhibitor comprises a phenol or quinone, a phosphine or an ester of phosphorous acid and a metal cation in the form of a salt or a complex which is soluble in the
polyester resin ( Holoch, J. and Eisenbirth, P.," Molding compounds of unsaturated polyester resins", Eur. Pat. 63.0.2484, 8 Feb., 1989) . Improving the flame retardar.t properties, unsaturated polyester based on terphthalic acid, 1,4 cyclohexane dimethanol, halogenated compounds and appiox. 2-8 wt. % powdered antimony metal of the total composition having a particle size of less than approx. 500 jam has been developed (Minnick, A.L., " Polyester molding compounds", Eur.Pat 030 46 35^ 1 March, 1989) . Effort to reduce the mould shrinkage, improved surface finish, extended shelf lives and enhanced toughness of dough molding sheet was made by the addition of various designed additives. Injection moulding by plunger type machine using this formulation was made. This development results in a more uniform distribution of reinforcement and filler in the molded parts, better physical strength due to freedom from voids and higher densification to suit the products in automobile industry and other applications (Collyer, A.A.,"Dough molding and sheet molding compounds", High performance. Plast. 4(4),1987, p. 1) . it is reported that several features of the screw injection process have advantages over the plunger type for volume production. In the screw injection process, cure cycles can be 10-25 % faster, shot control is more accurate with less flash and more consistent part quality and surface finish are obtained. The advantages of this process are weighted against potential differences in mechanical properties between material mould with the screw and plunger (Leopold, P.M.," Injection moulding of polyester bulk/ sheet molding compound ; screw/ plunger", Thermoset 90: meeting the challenge, Rosement Illinois, USA, 20-22 March 1990, p. 17) .
To reduce the weight of dough molding components, resin composition comprising "unsaturated polyester resin, polymerizable monomer, thermoplastic resin, initiator,hollow glass spheres of. a true density 0.5-1.3 g/cm3 and glass fibres has been developed. The molding materials have a superior workability and are useful for the production of automotive exterior body panels and other parts (Shibata, T., Miyashita, H., Aoki, S.; Akiyama,K.," Unsatu-urated polyester resin compositions, molding compounds and molded products therefrom", Eur.Pat^. 654 9827, July_jL993) . To speed up the production, a fully automatic injection/compression process for glass filled thermoset polyester bulk molding compound has been developed. The advantages of this process are cycle time reduction of upto 75% and low waste to part ratio over conventional compression moulding ( Battenfield, " Automatic moulding of polyester bulk molding compound ", CAN. Plast. 43 (9), 1985, p. 26). The high level toughness in exterior automotive parts based on polyester resin molding was obtained by developing a new composition comprising polyester blends based on dodecane dioic acid, vinyl monomer, thermoplastic low shrink control additives, reinforcing fibres, inner filler, metal oxide and a release agent (Michaels,J.B. , "Polyester resin molding composition", US Pat. 52 369 76, 17 Aug. 1993). Under material substitution, checker floor plates made from sheet/dough molding compound have been prepared for replacing steel and aluminium. They possess good fire and corrosion resistance properties alongwith high impact strength (ERF plastics, "Dough/sheet molding compounds", Br. Plast. Rubber, May 1987, p.n). Polyester molding composition containing glass fibre of approx. 0.05-3 mm
length, 4- methyl 2,4-diphenyl pentene and a transparent filler
has been developed. The molding gives glossy, transparent, thick,
pOrofile articles without cracking even at high temperature. It
can be used for the production of kitchen counters, bathtubs etc. (Okuno, T., Nakagauoa, N.,"Unsaturated polyester molding compounds and the product thereof", U.S. Pat. 3281633, 23 Jan. 1994) . In order to avoid fibre breakage, low work screws have been designed for injection moulding. Attempts to toughen dough molding compounds by modified resin matrix have met with little success (Gibson, A.G. and Pennington, D.," Seeking reinforcements to improve dough molding compound properties",Plast. Rubb. Wkly, 14 March 1987, p.30). Besides improving the machine design for dough molding compound, attempts have been made to replace glass fibres reinforcement by other fibres. Studies with polyethylene terphthalate/ glass fibres reinforcement showed that 10-25% of glass replaced by polyethylene terphthalate fibres,there were no severe deflashing difficulties and a worthwhile improvement in impact performance was obtainted with a modest cost increase. The fibre breakage was not noticed (Gibson, A.G. and Rennington, G. , " Polyethylene terphthalate fibre flow intact in dough molding compound ", Plast. Rubb. Wkly, 21 March 1987, p.15). Recently, dough molding materials reinforced with kevlar fibres have been introduced. Improved dimensional tolerance alongwith desired structural integrity was noticed due to kevlar's low mould shrinkage compared with thermoplastic polyester fibres (Freeman chemical, Du Pont de Nemours, " Reinforced dough compound", Eur. Plast. News, 15 (9), Sept.1988, p. 49) . Reduction in cost of dough molding compound
was made by adding wood flour while maintaining certain properties such as shrinkage and thermal stress curing curing. The tendency of using wood fibres in conjunction with glass fibres was also seen for non-structural applications. Wood fibres are much cheaper than glass fibres. The mixing of wood fibres in dough molding compounds has been enhanced through thickening the mix by using zinc oxide or by adding an increased amount of scrap polystyrene. As a result, the time needed for mixing and the requirement of expensive styrene have been reduced. Attempts to reduce the brittleness and increase in mechanical properties of the compounds by pretreating the fibres have not been successful (Frieschmidt, G. et al. , "Wood fibre-Polyester dough molding compounds", Polymer International, 24, 1991, p. 113). Earlier reports in literature reveal that most of the work has been concerned only on the use of glass fibres alongwith non-reinforcing mineral fillers in dough/ bulk molding compound and confined only to automotive sectors. Information on other reinforcements ,are very scanty. Attempts on improvement in various aspects of dough molding compound material properties such as cohesiveness of mixes, heterogeneity of 'constituents distribution (mixing), brittleness, structural integrity etc. are still debatable and unresolved. Seeking an alternative reinforcement in combination with fibrous fillers in dough molding compound compositions are imperative to develop cost-effective performance based products.
The main object of the present invention is to provide a novel molding composition which obviates the drawbacks as
Another object of the present invention is to provide novel molding composition wherein surface-modified natural fibres such as sisal, jute, coir, sunhemp etc. may be used.
Yet another object of the present invention is to provide a molding composition using fibrous reinforcing mineral filler such as surfied wolastonite of high aspect ratio (1/d 20 - 30).
Still another object of the present invention is to provide a molding composition containing a blend of vinyl monomers.
Another object of the present invention is to provide a process for making industrial products such as roof tiles, instrument panels, sanitary wares using the novel molding composition.
Accordingly the present invention provides a process for making industrial products using a novel molding composition comprising 30- 50 wt% unsaturated isophthalic based polyester resin selected from diethylene glycol, isophthalic acid and maleic anhydride, 9-15 wt% of methyl methacrylate, 8-20 wt% surface modified natural fibres selected from chopped sisal, jute, coir, sunhemp, 3-8 wt% chopped glass fibres, 30 - 45 wt%, surface modified wollastonite of aspect ratio (1/d) 20 -30 ,1
- 5 wt% zinc oxide, 0.5 - 3 wt% calcium stearate, 0.5 - 1.5 wt% benzoyl peroxide and 0.5 - 1.5 wt% cobalt naphthenate, said process comprises-*
surface modification of chopped natural fibres and wollastonite drying and
smerface modification by
coupling agent solution such as herein described, pre-mixing dry ingredients of the molding composition as described above, adding in stages wet components of the said molding composition at room temperature and mixing dry and wet components for a period of 10 - 60
minutes to obtain a dough, adding surface modified; fibre to the obtained
dough, allowing the dough to mature for 4 - 6 weeks in polyethylene bags and compressing the resultant dough in a mould of requisite industrial product, at a temperature in the range of 80 - 150°C and pressure in the range of 0.5 - 2 MPa for a period of 1 - 2 hours, curing the product in the mould at room temperature for at least 16 hours, followed by post-curing at a temperature in the range of 80 - 105°C for a period of 3- 5 hours at a pressure of 0.5 - 1 MPa, followed by removal of the product from the mould.
In an embodiment the unsaturated polyester resin used may be such as condensation product ofdiethylene glycol, isophthalic acid and maleic anhydride.
In another embodiment of present invention the surface modification of chopped natural fibres and wollastonite may be effected by immersing in 0.5-2 % (by ,,t. of fibres) solution of quaternized titanate (methacrylamide functional amine adduct of neopentyl (diallyl) oxy, tri (dioctyl) pyro-phosphato titanate) and silane coupling agent such as garama-methacryloxy propyl tri- methoxy silane to improve cohesiveness of the mix.
The novel molding composition of the present invention is not a mere admixture but a synergistic mixture having properties which are distinct from the mere aggregated properties of the individual ingredients.
Accordingly, the present invention provides a process for making industrial products using the novel molding composition, which comprises pre-mixing dry ingredients, adding in stages wet components at room temperature and mixing for a period of 10-60 minutes to obtain a dough, allowing the dough to mature for 4-6 weeks in polyethylene bags and compressing the resulted dough between male/female die of a mould of requisite induotrial product at a temperature in the range of 80-150°C and
pressure in the range of 0.5-2 MPa for a period of 1-2 hours, curing the product in the mould at room temperature for at least 16 hours, followed by post-curing at a temperature in the range of 00-105°C for a period of 3-5 houra at a pressure of 0.5-1 MPa, followed by removal of the product from the mould.
Accordingly, the present invention provides industrial products such an roof tilos instrument panols, sanitary wares
made using the novel molding composition and the process of the present invention.
The chopped natural fibres(3-6 mm) were thoroughly washed with water to remove maximum possible water solubles and subsequently placed in mild sodium hydroxide solution(10-20 gm/1) to remove waxy layers from the surface. These fibres were washed and dried in air and also in an air circulating oven at 105 + 2°C upto a constant moisture content. Prior to pretreatment, this may help to enhance the efficacy of coupling agent onto fibre substrate. The mercerised fibres were then immersed in 0.5-2wt.% quaternised titanate (methacrylamide functional amine adduct of pyro-phosphato titanate)coupling agent solution for surface modification purpose and is stirred continuosly for 30-60 minutes. Thereafter, the surface modified fibres were washed with water solvent to remove the excess of physisorbed compounds from the fibre surface. The treated fibres were dried at 80-110+2°C for 30-60 minutes to ensure the complete polymerization reaction. The selection of quaternizeu titanate coupling agent is made because of its cost-effectiveness, toxicity free and good compatibility with unsaturated polyester resin. Similarly, surface modification of wollastonite(1/d 20-30) was carried out by immersing it in 0.5-2 wt. % of silane coupling agent solution (gamma-methacryloxy propyl tri-methoxy silane)in benzene. The slurry was agitated for 2-3 hours and filtered on a buckner funnel. The treated sample was then washed with benzene to remove unreacted silane from the surface and dried at 80-100°C for 1-4 hours to complete the condensation reaction. The use of
silane coupling agent as surface modifier provides homogenous dispersion of wollastonite in the resin besides improving interfacial bonding between fibrous mineral and resin. The typical recipe for dough molding compounds are 30-50 wt. % styrenated isophthalic polyester resin, 9-15 wt. % methyl methacrylate / n-butyl methacrylate monomer, 0.5-1.5 % benzoyl peroxide(catalyst) and 0.5-1.5 % cobalt naphthanate(accelerator), 8-20 wt. % chopped natural fibres, 30-45 wt. % wollastonite, 1-5 wt.% zinc oxide, 0.5-3 wt. % calcium stearate and 3-8 wt.% chopped glass fibres in some cases. In the basic recipe of dough molding compound,mineral fillers and glass fibres have been replaced by wollastonite and natural fibres and their surface pre-treatments respectively. Vinyl monomer blends consisting of styrene-methyl methacrylate and styrene-n butyl methacrylate have been used instead of styrene monomer only. All the dry components of the formulation except fibres were mixed together in a mixer. Catalysed styrenated isophthalic polyester resin was prepared separately. The dry and wet components of recipe were mixed together to a paste for 10-60 minutes in a mixer. Subsequently, surface modified fibres were added into a mix over 10-30 minutes to ensure proper homogeniety. The resulting dough like material can be stored in a polyethylene bag for 4-6 weeks. These dough molding compounds were spread over mild steel/ brass plates and compressed in a hydraulic press. The plates of the press were heated upto 80-150°C for 1-2 hours under a pressure of 0.5-2 MPa depending on the viscosity of the mix. The plates were further allowed to cool. The curing of dough molding sheets was done at room temperature for 16-24 hours
and then post cured at 80-105°C for 3-5 hours at a pressure of 0.5-1 MPa. The demoulded sheets are saw cut and trimmed to form plates of desired size.
in porouanco oil diucuuuion on prior art, attempt has been made to develop a dough moulding compound based on other reinforcements to glass fibres. The chopped natural fibres along with fibrous wollastonite of high aspect ratio have been introduced into basic recipe of dough molding compound. This combination is also used in conjunction with glass fibres as synergist reinforcement to obtain functionally efficient recipe for making of better products. Processing benefits and hygrothermal stability of dough molding compound are improved by modifying the surface of natural fibres and wollastonite by thermoset polyester resin compatible coupling agents. Exploiting the drawback of natural fibres towards moisture
absorption, quaternized titanate (aqueous medium) was applied which mask the moisture attracting surface hydroxyl and other oxygen containing groups by long chain hydrocarbon attachment. The methacryl functionality of coupling agent provides good compatibility with resin matrix and formed a good fibre-matrix interface. Accordingly, wollastonite-polyester interaction is made by the attachment of the hydrolysable silanol groups of the silane with the silicate moiety of the mineral. On the other hand, pendent organic groups are free to interact with polymer and yield a good mineral-polymer bonding with improved dispersion and other benefits. Using vinyl monomer blends of atyrene-methyl methacrylate and otyrene-n butyl methacrylate, the
mould shrinkage, workability and durability of dough molding compound are improved. This blend will overcome the problems of compatibility with resin and mix viscosity occured due to addition of thermoplastic shrink control agent in the moulding. Dough molding sheets so obtained from this formulation are light weight, cost-effective and possessing somewhat comparative properties to glass fibre-dough molding sheets (values of various properties were taken from literature for comparision).
The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention.
40 gms of chopped sisal fibres (6 mm) were washed with distilled water and immersed in 2 wt.% sodium hydroxide aqueous solution for 1 hour. After 15 minutes immersion in solution, the fibres were taken out, washed with distilled water and dried at 105 + 2°C upto a constant moisture content. These mercerized fibres were further dipped in 1% (by wt. of fibre) quaternised titanate coupling agent solution and stirred continuously for 30 minutes. Subsequently, surface modified sisal fibres were washed with water to remove loosely bonded compounds and dried at 110°C for half an hour. Similarly, surface treatment of 130 gms wollastonite (1/d 20-30) was carried out by immersing it in 1 % methacryloxy propyl tri-methoxy silane (by wt. of wollastonite) in benzene. The slurry was agitated for 2 hours, 'filtered on a buchner funnel and washed with benzene. The surface-treated
wollastonite was dried at 80°C for 4 hours and stored in polyethylene bags. The typical recipe of dough molding compound consisting of 34 wt. % styrenated isophthalic polyester resin, 12 wt. % methyl methacrylate, 12 wt. % chopped sisal fibres, 39 wt. % wollastonite, 1 wt. % zinc oxide, 0.5 wt. % calcium stearate, l.5wt.% benzoyl peroxide(catalyst) and 1.5wt.% cobalt naphthenate (accelerator) has been formulated. The dry components of formulation except fibre were mixed together in a mixer. Separately, wet components of dough molding compound such as 34 wt. % styrenated isophthalic polyester resin, 12 wt.% methyl methacrylate, l.5wt.% benzoyl peroxide (catalyst) and 1.5wt.% cobalt naphthenate (accelerator) were also prepared. The dry and wet components of formulation were mixed together for 30 minutes in a mixer followed by the addition of surface-treated sisal fibres. The mix was continuously operated for 10 minutes. After ensuring homogenous mixing, dough like material has resulted and stored for 4 weeks in a polyethylene bag. During casting of sheet (8"x8"); dough molding compound was placed between two brass plates and compressed in a hydraulic press for 2 hours under a pressure of 0.5 MPa at 150°C. The plates were further allowed to cool at room temperature for 24 hours and then post-cured at 80°C for 4 hours at a pressure of l MPa. The demoulded sheets were trimmed to form a plate of desired size. The properties of dough molding sheets are given in Table 1.
Comparative properties of Sisal- molding compound and Glass-molding compound
30 gms of chopped sisal fibres of size 6 mm were washed with distilled water and immersed in 2 wt. % sodium hydroxide aqueous solution for 1 hour. After 15 minutes immersion in solution, the fibres were taken out,washed with distilled water and dried at 105+ 2°C upto a constant moisture content. These mercerized fibres were further dipped in 1%(by wt. of fibre)quaternized titanate coupling agent solution and stirred continuously for 30 minutes. Subsequently, surface modified sisal fibres were washed with water to remove loosely bonded compounds and dried at 110°C for half an hour. Similarly, surface treatment of 115 gms wollastonite(1/d 20-30)was carried out by immersing it in 1% methacryloxy propyl tri-methoxy silane(by wt. of wollastonite) in benzene.The slurry was agitated for 2 hours, filtered on a
buchner funnel and washed with benzene. The wollastonite was dried at 80°C for 4 hours and stored in poyethylene bags. The typical recipe of dough molding compound is given in Table 2a.
Polyester molding composition
Ingredients Percent by weight
Chopped sisal fibres 9
Sized chopped glass fibres 4
Zinc oxide 1
Calcium stearate 0.5
Quaternized titanate 1
(% wt. fibre)
Methacryloxy silane 1
(% wt. of wollastonite)
Styrenated isophthalic 40
n-butyl methacrylate 10
Benzoyl peroxide 1.5
Cobalt naphthenate 1.5
The dry components of the formulation except sisal and glass fibres were mixed thoroughly. The wet components of recipe such as 40 wt.% catalysed isophthalic polyester resin, 10 wt.% n-butyl methacrylate monomer, 1.5 wt.% benzoyl peroxide (catalyst) and 1.5 wt.% cobalt naphthenate (accelerator) were prepared separately. The dry and wet components of compound were mixed thoroughly in a mixer resulting in a paste. Subsequently, sisal fibres (9 wt. %) were added while mixing the constituents. After
20 minutes, chopped glass fibres of size 6 mm (4 %) was further incorporated. Flat sheet of size 8"x8" was prepared using this dough molding formulation. The material was placed between two brass plates, levelled carefully and pressed under a hydraulic press for 1 hour under a pressure of 1 MPa at 130°C. The curing of sample was done at room temperature for 16 hours and then post-cured at 80°C for 4 hours at a pressure of 1 MPa. The demoulded sheets were trimmed to form a plate of desired size.The properties of dough molding sheets are given in Table 2b,
Comparative properties of Sisal/Glass-molding compound and Glass-molding compound
Tensile Strength(MPa) 42.28 30-60
Elongation(%) 0.65 0.34
Tensile modulus(GPa) 7.80 6-8
In conclusion, natural fibres and wollastonite with proper resin compatible pretreatments could be effectively used as a synergist reinforcement alternatives to glass fibres in the development of dough molding compounds.The dual functionality of surface-modified wollastonite in replacing completly traditional mineral fillers such as A1203, CaCO3 etc. and also importantly substituting partially/solely glass fibres by its reinforcing ability make the dough molding products cheaper and more
attractive in automotive and construction markets. It is also noticed that methyl methacrylate monomer in conjunction with styrene not only enhance the workability of mix but also improve durability of dough moulding compounds.
The main advantages of the novel molding composition of the present invention are:
1. Light weight
2. Long shelf life
3. Good workability
4. Good mechanical properties
5. Better weatherability
6. Corrosion resistance
7. Good insulation properties
9. Alternative to glass fibre based dough molding compound
10. Could be used as replacement to metals in many applications
1. A process for making industrial products using a novel molding composition comprising 30- 50 wt% unsaturated isophthalic based polyester resin selected from diethylene glycol, isophthalic acid and maleic anhydride, 9-15 wt% of methyl methacrylate, 8-20 wt% surface modified natural fibres selected from chopped sisal, jute, coir, sunhemp, 3-8 wt% chopped glass fibres, 30 - 45 wt%, surface modified wollastonite of aspect ratio (1/d) 20 -30 , 1 - 5 wt% zinc oxide, 0.5 - 3 wt% calcium stearate, 0.5 - 1.5 wt% benzoyl peroxide and 0.5 - 1.5 wt% cobalt naphthenate, said
process comprises, alkali treatment of chopped natural fibres
and wollastonitedrying and smface modification by coupling agent solution such as herein described, pre-mixing dry ingredients of the molding composition as described above, adding in stages wet components of the said molding composition at room temperature and mixing dry and wet components for a period of10 - 60 minutes to obtain a dough,
adding surface modified natural fibre to the obtained dough, allowing the dough to mature for 4 - 6 weeks in polyethylene bags and compressing the resultant dough in a mould of requisite industrial product, at a temperature in the range of 80 - 150°C and pressure in the range of 0.5 - 2 MPa for a period of 1 - 2 hours, curing the product in the mould at room temperature for at least 16 hours,
followed by post-curing at a temperature in the range of 80 - 105°C
for a period of 3- 5 hours at a pressure of 0.5 - 1 MPa, followed by
removal of the product from the mould.
2. A process as claimed in claims 1, wherein the alkali treatment of chposed
natural fibbers and wall ostonite is effected by treatins with sodium hydroxide
(2%wt) and surface modification is effected by immersing
in 0.5 -2% (by wt. of fibres) solution of quanternized titanate ( methacrylamide functional amine adduct of neopentyl (diallyl) oxy, tri (dioctyl) puro-phosphato titanate) and silane coupling agent such as gamma-methacryloxy propyl tri-methoxy silane.
3. A process for making industrial products using a novel molding
composition substantially as herein described with reference to the
|Indian Patent Application Number||3321/DEL/1998|
|PG Journal Number||10/2008|
|Date of Filing||09-Nov-1998|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001|
|PCT International Classification Number||C08K 13/01|
|PCT International Application Number||N/A|
|PCT International Filing date|