|Title of Invention||
PROCESSING AIDS FOR HALOGENATED POLYMERS AND COPOLYMERS
|Abstract||Nitrated polystyrene and/ or ketonic resin is disclosed as processing aid for halogenated polymers and copolymers, particularly PVC. Further PVC composition comprising the processing aids like nitrated polystyrene and/ or ketonic resin with improved rheological properties facilitating processibility of PVC is also disclosed herein.|
|Full Text||FORM 2
THE PATENT ACT 1970
(39 of 1970)
The Patents Rules, 2003
(See section 10 and rule 13)
1. TITLE OF THE INVENTION: Processing aid for halogenated polymers and copolymers.
2. 2 APPLICANT
(a) Name : Malshe Vinod Chintamani
(b) Nationality : Indian
(c) Address : 1, Staff Quarters, UDCT Campus, Matunga,
Mumbai - 400 019, Maharashtra, India
(a) Name : Malshe Vinod Chintamani
(b) Nationality : Indian
(c) Address : 1, Staff Quarters, UDCT Campus, Matunga,
Mumbai - 400 019. Maharashtra, India
(a) Name : Patil Jagdish LiLadhar
(b)Nationality : Indian
(c) Address : 1, Staff Quarters, UDCT Campus, Matunga, Mumbai - 400 019. Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.
The present invention relates to processing aids for halogenated polymers and copolymers. Particularly, the present invention relates to nitrated aromatic polymer or oligomer or ketonic resin or combination thereof as processing aid, which is stable at processing temperature, and improves rheological properties facilitating processibility of halogenated polymers and copolymers such as polyvinyl chloride (PVC) and improving the flow of halogenated polymers and copolymers such as PVC. The present invention also relates to PVC compositions comprising the above processing aids.
Background and Prior art:
Processing aids have been used commercially in PVC compounds from many years. Processing aids influence the melting and recrystallization kinetics of the PVC crystallites. The physical and processing properties of these polymeric additives are blended with those of the PVC matrix to better suit the fabrication or end use requirements. PVC has a well-defined molecular structure, which is very difficult to destroy at temperatures below the degradation point. The rheological characteristics of PVC melts are determined by this molecular structure and the mechanism of action of processing aids is related to their effects on these crystallites flow process. Processing aids accelerate and control the fusion process in PVC compounds and they strongly affect the rheological characteristics of the fully fused PVC melt.
The effect of a processing aid on the processing of a rigid PVC powder blend could be observed during the plasticization/fusion process. The processing aids greatly shorten the time and the heat/shear history necessary to melt and homogenize the compound. In simple laboratory experiments on two-roll mills, addition of a processing aid shortens the time required to flux the powder blend to form a homogeneous band with smooth edges, and develop a uniform rolling bank. Modern laboratory test equipment, instrumented kneader mixers such as the Brabender and Haake machines, gives more accurately determined effects of processing aids on the fusion characteristics of PVC compounds
and the viscosity data of the melts. When running a predetermined quantity of PVC powder blend under a controlled temperature and speed conditions, the recorded evolution of the torque needed to turn the blades as a function of time gives a direct measure of the fusion process. The point of maximum torque is generally accepted as representing the beginning of plastification. During the fusion process maximum torque increases considerably, reflecting the increased interaction of the PVC particles with each other and with the chamber surfaces.
Unmodified rigid PVC compounds are notably poor in this respect, in particular, when processed at low to moderate temperatures, the crystalline regions in the primary PVC particles do not melt and the degree of molecular interdiffusion between particles is very low, so the interparticle strength is very poor. The most important function of processing aids in rigid PVC is the improvement of the rheological characteristics-homogeneity, strength and elasticity of the melt after fusion and during fabrication. In this situation, the molecules of the processing aid function to bind together the particles and improve melt strength. In the case of the most widely used acrylic processing aids, their ability to perform this function is based on three inherent characteristics: Excellent compatibility with PVC, Flexible elastic characteristics of the acrylic polymer chains and High molecular weight polymer chains.
Processing aids continue to provide a strong enhancement of melt strength because they mix intimately with the shorter, stiffer PVC chains and provide a longer-range viscoelastic network. This network greatly assists in binding together the PVC domains, equalizing stress concentrations within the melt during fabrication and thus greatly reducing processing defects such as surface roughness, extrusion marks (lines), dragon teeth and scaling.
Processing aids show homogenizing action by tying together the semi-crystalline PVC domains into a more uniform viscoelastic structure. Thus they produce smooth rolling bank, well knit edges, uniform and glossy surface. This effect is the key to successful production of a high quality surface in high-speed rigid PVC calendaring. In addition, the
homogenization effect is important in extrusion processes for uniform delivery of constant quality and quantity of melt to the dies. Similarly in injection molding, this homogenization effect is important in obtaining good quality surfaces and avoiding weakness at weld lines. In all types of processes, the processing aids assist in binding together the myriad formulation ingredients to avoid plate out and so forth.
The most important reason for adding processing aids to rigid PVC compounds is to improve the elasticity and extensibility of the melt. This effect can be observed even in simple laboratory experiments such as milling by observing improvement in tear strength and extensibility. Various laboratory tests have been developed to measure the improved elasticity. One approach is simply to increase extrusion haul-off speed until the point is reached where the extrudate begins to tear or crack. Petrich [Petrich, Reprints, Plastics & Rubber Institute Conference on Processing of PVC, London, April 1978] used the Rheotens to compare the melt strength and elongation effects. Pazur and Uitenham (Pazur, A., and Uitenham, L., Soc. Plast. Eng. ANTEC Prepr., 573 (1981)) used the Gottfert Rheotens to study the effect of processing aid on the melt extension properties of a twin-screw PVC pipe compound. They showed that the addition of processing aid progressively increased the tensile viscosity of the compound at any given elongation.
Although processing aids normally raise the melt viscosity of PVC compounds slightly, a key factor in their success is that this effect is far smaller than their beneficial effect on melt elasticity /extensibility. The increase in viscosity actually depends on the viscosity of the base formulation and on the test being used. Ryan [Ryan, C, Soc. Plast. Eng. J., 24, 89 (1968)] found that the melt viscosity of a high-molecular-weight PVC compound measured in a capillary rheometer, increased only slightly over a broad range of temperatures and shear rates when an acrylic processing aid was added. This is possible because the typical molecular weight of acrylics used is in the range of 106 to 107 Dalton.
The use of plasticizers was the earliest attempted solution to the problems of inherently poor processing of PVC. A variety of low molecular weight chemical compounds were
found to be sufficiently soluble and mobile to penetrate the PVC structure, allowing it to soften at considerably lower temperatures. Thus, the minimum acceptable processing temperature was lowered considerably. However these plasticizers also caused a sharp reduction of the modulus and strength of PVC, even at low concentrations. Nevertheless, the resulting material had a useful balance of properties and found extensive commercial use.
During the 1950s it was found that some high molecular PVC-compatible polymers could function in this way. The first commercial processing aid for rigid PVC was Paraloid K-120, available to PVC compounders. US 2,646,417 and US 2,791,600 disclose processing aid such as copolymers of styrene with acrylonitrile or methyl methacrylate respectively. US3,485,775 describes the first commercially promoted processing aids, introduced by Rohm and Haas Company in the late 1950s, were of the acrylic type, that is, methacrylate/acrylate copolymers with methyl methacrylate predominating. Many acrylic monomers are available, and they can be combined in various ratios and structures, as well as in polymers of different molecular weights, so that a wide variety of acrylic processing aids can be tailored to any application desired. These various combinations have been the subjects of many patents like US 3,373,229, US 3,764,638, US 3,485,775, US 3,874,740, etc. Outside the acrylic field, poly (2-methyl styrene) has been used somewhat in commercial PVC applications [Wilson, A. and Raimondi, V. Reprints of PRJ Conf on Proc. Of PVC, London, April 1978]. Newer compositions suggested by US 4,137,280, but not yet used in significant volume, include poly (neopentylene terephthalate) and poly (alkylene carbonate).
In addition to conventional processing aids, US 3,859,384 and 3,859,389, Graham, R. J. Am. Chem, Soc, 34, 172 (1974) reported many multipurpose materials like class of lubricating processing aids, which combine external lubrication effects with the conventional rheological improvements of acrylic processing aids. Besides such commercial additives, similar principles have been applied to internal modification of PVC resins during their production to give easy processing lubricated resins as reported in US 4,051,200. Other experimental multipurpose processing aids have been tested but
without extensive commercial use to date. These include processing aids, which reduce the viscosity of the PVC compound like both acrylic [DE 2,163,986, US 3,859,384 and US 3,859,389] and polyester compositions. Other compositions have been designed to improve the thermal stability of the PVC compound through incorporation of glycidyl methacrylate functionality as described in US 3,096,313 or oxirane functionality as described in Rohm & Haas, 1966. Lastly, the possibility of raising the heat distortion temperature of PVC compositions has been suggested through the use of processing aids incorporating methacrylate copolymers with bicyclic side chains [US 3,485,775] or styrene/acrylonitrile/acrylamide terpolymers [US 3,584,079].
Although the ketonic resins have been known for a long time, new types of resins and new areas of application are always being found. These fields provide a wide scope for investigation as a good property variation can be achieved with the use of different raw materials in a fixed proportion or the same raw materials used in different proportions.
The ketonic resins are obtained either by self-condensation or more frequently co-condensation with formaldehyde. Other monomers such as phenol and urea are also sometimes incorporated. The condensation of monomers can be accelerated using basic, acidic or neutral catalyst. Basically ketonic resins can be of three types.
Product obtained by reacting lower molecular weight aliphatic or aromatic ketones such as acetone or methyl ethyl ketone, cyclopentanone, acetophenone or cyclohexanone with formaldehyde. In this condensation of ketone with formaldehyde basic catalysts play the major role. The reaction follows the mechanism of aldol condensation and leads to aldol type products and after elimination of water produces oligomeric compound.
Polycyclic resins made by alkali-catalyzed self-polymerization of a cyclic ketone such as cyclohexanone or methyl-cyclohexanone. Polymers made by vinyl polymerization of an unsaturated ketone such as methyl vinyl ketone or methyl isopropyl ketone.
Cyclohexanone formaldehyde resin was prepared from cyclohexanone and formaldehyde [Chemical Abstract Number 82:100278h] and used as an additive to enhance the coating properties of many resin systems [JP7,513,415, Chemical Abstract Number: 114:230782h, HU 52,139, Chemical Abstract Number: 115:210284q].
Patents were issued for the use of cyclohexanone formaldehyde (ketonic resin) as an additive to improve coating properties of alkyd resins [Chemical Abstract No. 115:210376w, Chemical Abstract No. 101:132673k, HU 29, 441].
A. J. Norton and his co-workers synthesized resinous product by carrying out reaction of cyclohexanone and formaldehyde in molar ratio of 1.6: 1 in cyclohexane, 20% sodium hydroxide as catalyst. The reaction gave resinous product at 70-75°C.
S. Patil and his co-worker [Paint India, 43(9), 15-16, 18-20, (1993)] synthesized ketonic resin by reacting cyclohexanone with paraformaldehyde in 1: 1.2 molar ratio using sodium hydroxide catalyst. This resin had high melting point, good solubility and viscosity, which was suitable for printing inks.
Ketonic resin was prepared by using alkali catalyst by suspension polymerization of cyclohexanone with formaldehyde [Chemical Abstract No. 100:140199, RO 71853]. Using carboxy methylcellulose as a dispersing agent and 1-15% sodium chloride salting-out agent and regulating the organic-aqueous phase ratio at 1:4, particle-size distribution of the resin was controlled.
Alter [Chemical Abstract No. 87, 6875, DD 122389] prepared finely divided cyclohexanone-formaldehyde resin by a continuous process. Ketonic resin prepared from cyclohexanone and formalin was used for printing inks to improve gloss, adhesion and wettability and to raise the nonvolatile content.
Kunert [Chemical Abstract No. 100:8707] prepared coatings resistant to corrosion and stress cracking by using ketonic resin. These coatings are claimed to be useful on application in pipes, and steel in the chemical industry.
The addition of 2.5-25 phr cyclohexanone-formaldehyde copolymer [Gonzalez Lopez, A.; Chemical Abstract, 99: 71487] to a PVC formulation containing dioctyl phthalate, tribasic lead sulfate, and paraffin wax had a slight plasticizing effect, improved the resistance to thermal aging, and increased the bulk resistivity.
Aromatic polymers have been chemically modified to derive new products by several researchers. In many cases these modifications are done on the lines of simple organic molecules, generally to derive functional polymers. Nitration of polystyrene is one such example. It has been accomplished with no specific end use in mind by several researchers.
Nitrated polystyrene [Chemical Abstract 133:59269, RO 112623] having N02 groups on the polymer chain and benzene ring was prepared by heating polystyrene for 120-180 minutes in 50-70% HN03 at 80-120° and polystyrene medium ratio 1:(7-10) in the presence of 0.1-5% ZnC12 or Zr (N03) 4, cooling to 15-20°C, decanting the product as semi viscous material, washing with water, boiling, decanting again, neutralizing with 0.5-1% NH3 solution, drying at 80-85°C.
Polystyrene was nitrated [Chemical Abstract 116: 21633] at 15°C using nitrating agents such as mixture of concentrated nitric and sulfuric acid without an organic solvent or nitric acid and acetic acid mixture in chloroform.
Polystyrene was subjected to nitration [Chemical Abstract 116:236951] with nitric-acetic acid mixture in carbon tetrachloride followed by reduction with SnC12 to prepare aminated polystyrene having regulated degree of NH2 group.
Philippides et al [Polymer, 34(16), 3509-13, (1993)] compared four methods for the
nitration of polystyrene (i) direct nitration with a nitric acid/sulfuric acid mixture, (ii) nitration in carbon tetrachloride with acetyl nitrate, (iii) nitration in N, N'-dimethyl formamide with a nitric acid/sulfuric acid mixture and (iv) nitration in 3-nitrotoluene with a nitric acid/sulfuric acid mixture. The first 3 methods give products with low degrees of substitution and lead to a broadening of the molecular weight distribution, but the fourth method gives poly (4-nitrostyrene) with minimal effect on the breadth of the molecular weight distribution.
Porous polystyrene [Chemical Abstract 86:90894, JP 51138792] resins were nitrated with HN03 and trifluoromethanesulfonic acid to give nitrated porous polystyrene resins. Thus, 4.5 g of a porous divinylbenzene-styrene copolymer powder was stirred at 5-7° C with a mixture of 50 gm trifluoromethanesulfonic acid and 6.3 g nitric acid, poured into an ice water, rinsed with warm water and ethanol, and vacuum evaporated to give 5.7 g of a brown resin (41% nitration). The brown resin showed good chromatographic separation properties.
India produces over 5000 tons of expanded polystyrene which is not recycled and another 5000 tons get used as disposable thermoformed cups and packaging. None of these get recycled due to their very large volume and the difficulty in handling. Nitration of this polymer is possible due to presence of halogenated solvents, which are true solvents to polystyrene and copolymers.
Most of the commercial processing aids are based on methyl methacrylate copolymers. The solubility parameter of a polymer is an essential pointer to the selection of suitable processing aid for a polymer. The existing processing aids are not true solvents for the polymers and thus are not able to completely separate the chains. The viscosity of the polymer melt does not attain lowest value. Therefore there is need to have polymers with chemical structure which is chemically identical to the true solvents for PVC. PVC due to a highly steareoregular structure is highly crystalline and has very limited solvents.
An object of the invention is to provide processing aids selected from nitrated aromatic polymers or oligomers such as nitrated polystyrene or ketonic resin selected from acetophenone/ Formaldehyde or cyclohexanone / formaldehyde or combination thereof for halogenated polymers and copolymers.
Another object of the invention is to provide use of nitrated polystyrene as processing aids, which gives an alternative route for recycling waste polystyrene foams and teacups produced and wasted in large volume and tonnages.
Another object of the invention is to provide PVC compositions comprising the above processing aids with improved rheological properties facilitating processibility of PVC.
According to the invention there is provided processing aids for hlogenated polymers and copolymers, the processing aids comprising a nitrated aromatic polymer or oligomer or aliphatic or aromatic ketonic resin or combinations thereof.
According to the invention there is also provided PVC composition comprising a PVC resin and a processing aid selected from a nitrated aromatic polymer or oligomer or aliphatic or aromatic ketonic resin or combinations thereof along with the other conventional additives with improved rheological properties facilitating better processibility of PVC.
Particularly the processing aid for halogenated polymer and copolymer is Nitrated polystyrene or any suitable nitrated aromatic polymers or oligomers.
Particularly the processing aid for halogenated polymer and copolymer is cyclohexanone-formaldehyde or acetophenone-formaldehyde resin or any suitable aliphatic or aromatic ketonic resin.
A stable procesing aid selected from Nitrated polystyrene or any aromatic polymer or oligomer containing a nitro aromatic group derived by nitration, esterification or any other reaction leading to inclusion of a nitro group on the side chain of the polymer for halogenated polymer and copolymer.
The nitrated polystyrene is used in the range of 0.2 to 10 phr as processing aids in halogenated polymer or copolymer.
The ketonic resin is used in the range of 0.2 to 10 phr as processing aids in halogenated polymer or copolymer.
The halogenated polymer and copolymer is preferably polyvinyl chloride (PVC), Polyvinyl dichloride (PVDC) or polyvinyl difluoride (PVDF).
The other conventional additives are lubricants such as stearic acid, inorganic salt of stearic acid such as calcium stearate, zinc stearate, PE wax, paraffin wax; processing aids such as copolymers of different acrylates; thermal stabilizers such as tin stabilizer or lead stabilizers or mixed metal stabilizers based on calcium, barium, etc.
According to the invention there is also provided the PVC composition comprising 100 parts PVC, 0.5 part stearic acid, 0.5 part PE wax, 2 parts Tin stabiliser-AL and 4 parts of nitrated polystyrene.
According to the invention there is also provided PVC compositions comprising 100 parts PVC, 0.5 part stearic acid, 0.5 part PE wax, 2 parts Tin stabiliser-AL, and 4 parts Ketonic resin.
According to the invention there is provided use of a nitrated aromatic polymer or oligomer or aliphatic or aromatic ketonic resin or combinations thereof as a processing aid for halogenated polymer or copolymer for improved improved rheological properties facilitating better processibility.
A process for preparing nitrated polystyrene comprises preparing 20 % solution of polystyrene or polystyrene waste in chloroform, maintaining the temperature at 5-10°C with constant stirring, adding mixed acids comprising sulfuric acid and nitric acid in 1:1 molar ratio drop wise while cooling and maintaining the reaction mixture to -10°C within an hour followed by raising the temperature to 20°C; stirring the reaction mixture slowly and maintaining the temperature at 20°C for 3 hrs; obtaining clear straw colored viscous liquid of nitrated polystyrene at the end of the reaction; precipitating the polystyrene in the form of threads by adding the viscous liquid in methanol through dropping funnel under constant stirring; washings nitrated polystyrene with water several times to remove any traces of acids and drying the product, nitrated polystyrene, at room temperature.
The polystyrene waste is selected from sprues of injection molding process, off cut from vacuum forming sheets, scrap obtained from recyclable plastic components, thermocole (expanded polystyrene foam), etc.
The process for the synthesis of nitrated polystyrene is reported in the literature [Zenftman, H. J. Chem. Soc, 982. (1950)]. Presence of-N02 group was confirmed by organic qualitative analysis and FTIR spectroscopy.
The ketonic resin is prepared from acetophenone and formaldehyde by conventional method.
Synthesized nitrated polystyrene and ketonic resin is used as processing aid in the halogenated polymer and copolymer, particularly PVC.
Both nitrated polystyrene (NPS) and ketonic resin (KR) were compounded with PVC along with other additives and further extruded as a sheet as per the conventional method. Particularly a polyvinyl chloride molding composition was prepared by blending polyvinyl chloride with the processing aids like ketonic resin and / or nitrated polystyrene along with conventional additives in a high speed mixer for 10 minutes at 1200 rpm. The blend was then processed in Brabender Twin Screw counter rotating extruder at 160 -164°C and 45 rpm. The compounds were extruded into sheets of 1 mm thickness and then pulled through a series of three heated steel rollers at 80°C temperature.
Table 1 gives typical formulations used for compounding of extruded sheet. Rheological and mechanical properties of the compounds were evaluated using the standard methods.
Table: 1 Processing of Rigid PVC
K-400 NPS KR PVC (Blank)
PVC 100 100 100 100
Steric Acid 0.5 0.5 0.5 0.5
PEWax 0.5 0.5 0.5 0.5
Tin Stab-AI 2 2 2 2
Processing Aid (K-400) 4 - - -
Nitrated Polystyrene - 4 - -
Ketonic Resin - - 4 -
The invention is further illustrated by the following examples, which should not construe the effective scope of the claims.
Blank PVC composition
A polyvinyl chloride molding composition was prepared by blending 100 weight parts of the polyvinyl chloride, 0.5 parts of a stearic acid, 0.5 parts of a PE wax, and 0.25 parts of a Tin-stabilizer-Al in a high speed mixer for 10 minutes at 1200 rpm. The blend was then processed in Brabender Twin Screw counter rotating extruder at 160 - 164°C and 45 rpm. The compounds were extruded into sheets of 1 mm thickness and then pulled through a series of three heated steel rollers at 80°C temperature.
PVC Composition with Nitrated polystyrene (NPS)
A polyvinyl chloride molding composition was prepared by blending 100 weight parts of the polyvinyl chloride, 0.5 parts of a stearic acid, 0.5 parts of a PE wax, 0.25 parts of a Tin-stabiliser-Al and 0.4 parts Nitrated polystyrene as processing aid (NPS) in a high speed mixer for 10 minutes at 1200 rpm. The blend was then processed in Brabender Twin Screw counter rotating extruder at 160 - 164°C and 45 rpm. The compounds were extruded into sheets of 1mm thickness and then pulled through a series of three heated steel rollers at 80°C temperature.
PVC Composition with Ketonic resin (KR)
A polyvinyl chloride molding composition was prepared by blending 100 weight parts of the polyvinyl chloride, 0.5 parts of a stearic acid, 0.5 parts of a PE wax, 0.25 parts of a Tin-stabiliser-Al and 0.4 parts ketonic resin as processing aid (KR) in a high speed mixer for 10 minutes at 1200 rpm. The blend was then processed in Brabender Twin Screw
counter rotating extruder at 160 - 164°C and 45 rpm. The compounds were extruded into sheets of 1mm thickness and then pulled through a series of three heated steel rollers at 80°C temperature.
PVC Composition with commercial acrylic processing aid (KR-400)
A polyvinyl chloride molding composition was prepared by blending 100 weight parts of the polyvinyl chloride, 0.5 parts of a stearic acid, 0.5 parts of a PE wax, 0.25 parts of a Tin-stabiliser-Al and 0.4 parts commercial acrylic processing aid as processing aid (KR) in a high speed mixer for 10 minutes at 1200 rpm. The blend was then processed in Brabender Twin Screw counter rotating extruder at 160 - 164°C and 45 rpm. The compounds were extruded into sheets of 1mm thickness and then pulled through a series of three heated steel rollers at 80°C temperature.
The sheet obtained by the four examples was studied for their properties like rheological parameters of compounded PVC by Barbender Plastograph, rheology and mechanical, which are given below.
Properties of Processing Aids
Formulation k-400 contains standard commercial acrylic processing aid, NPS contains synthesized nitrated polystyrene and KR contains commercial ketonic resin. Processing aids like standard commercial acrylic processing aid, nitrated polystyrene, ketonic resin were added at 4-phr doses in all the formulation except PVC, which was the blank. Brabender Plastograph gave the torque required during processing of the compound. Lower the torque, lower will be the viscosity. The effect of processing aid on the processing of rigid PVC can be observed during the fusion process. The point of maximum torque is generally accepted as the beginning of fusion, above which torque begins fall. As can be seen from Figure 1, as compared to blank (without any processing
aid), all other compounds show maximum torque at shorter time. The reduction in time was from 60 seconds to 30 seconds for compounds containing processing aid. Among these processing aid there was not much change in time for developing maximum torque. Maximum torque was considerably increased due to processing aid reflecting the increased interaction of the PVC particles and the chamber surfaces.
Further it was observed that blank compound started degrading and formation of the sheet of this compound was difficult whereas compounds containing processing aids processed well without any degradation thus providing required processing window.
Figure 2 and Table 2 show rheological data of PVC compounds containing processing aids. It was difficult to analyze rheological data of virgin PVC as it degrades severely during the analysis. Figure 2 shows that inclusion of processing aid into the compound reflects in their favorable rheological behaviour. All the compositions were shown well defined zero shear viscosity at very low shear rates. Among the three processing aids, NPS showed sharp drop in viscosity with increase in shear rate. In the Newtonian or zero shear range NPS offers much lower viscosity as compared to other two. In fact NPS offers lowest viscosity and least resistance to flow. NPS and KR both showed reduced viscosity as compared to its standard, acrylic (K-400) based processing aid by a factor of 2 to 4. NPS and KR reduce the melt viscosity and show the improvement in flow properties of compounded PVC, which indicates ease of processing.
Table 2 Rheological data of PVC compounds
Stabilizer 0.01 0.05 0.1 0.5 1
NPS 69183 24690 15300 5982 4392
KR 88550 33720 23070 10600 6485
K-400 126600 56850 40840 16780 -
Table 3 shows mechanical properties of the PVC compounds containing different processing aid. Addition of K-400 slightly changed the flexural modulus. However overall mechanical properties were not affected much by the addition of processing aid.
Table: 3 Mechanical Properties of PVC compounds
Sample Flexural Modulus (Mpa) Flexural Strength (MPa) Tensile Strength (MPa)
K-400 11720 57.57 47.84
KR* 12705 55.34 45.13
NPS# 12750 56.58 45.42
*- ketonic resin #- nitrated polystyrene polymer
Description of the accompanying drawings
Figure 1 illustrates Brabender Plastograph of PVC compound with without processing aid along with other suitable additives. In this x-axis (1) indicates time in minutes against Y axis (2) indicates torque obtained in (Nm). As compared to blank (without any processing aid) (5), all other compounds (3, 4 and 6) showed maximum torque at shorter time. The reduction in time was from 60 seconds to 30 seconds for compounds containing processing aid. Among these processing aid there was not much change in time for developing maximum torque.
Figure 2 illustrates rheology of PVC compounds containing different processing aids at 180° C. In this X-axis (7) indicates shear rate (1/s) against Y-axis (8) indicates shear viscosity (Pas). All the compositions (9, 10 and 11) were shown well defined zero shear viscosity at very low shear rates. Among the three processing aids, NPS (11) showed sharp drop in viscosity with increase in shear rate. In the Newtonian or zero shear range NPS offers much lower viscosity as compared to other two (9 and 10). In fact offers lowest viscosity and least resistance to flow. NPS (11) and KR (10) both showed reduced viscosity as compared to its standard, acrylic (K-400) (9) based processing aid by a factor of 2 to 4. NPS (11) and KR (10) reduce the melt viscosity and show the improvement in flow properties of compounded PVC, which indicates ease of processing.
Thus the invention provides nitrated polystyrene and / or ketonic resin as processing aid for halogenated polymer and copolymer, particularly PVC. Further the Nitrated polystyrene found to be stable at processing temperature of PVC. The Processing aid was synthesized by simple nitration of polystyrene and dose not requires stringent conditions and can be carried out at ambient conditions. The invention further provides PVC compositions comprising processing aid with improved rheological properties facilitating the processibility of PVC compounds. Their performance was found to be better than the commercial acrylic based processing aid. Mechanical properties of the compounds were not affected by addition of processing aids. By using Nitrated polystyrene as processing aid in PVC, the invention also gives a viable route to utilize waste polystyrene to convert into value-added products. This can also make the processing aid commercially attractive due to low cost.
1. A stable processing aid for hlogenated polymers and copolymers, the processing aids comprising a nitrated aromatic polymer or oligomer or aliphatic or aromatic ketonic resin or combinations thereof.
2. The processing aid as cliamed in claim 1, wherein the nitrated aromatic polymer or oligomer is nitrated polystyrene.
3. The processing aid as cliamed in claim 1, wherein the aliphatic or aromatic ketonic resin is cyclohexane-formaldehyde or acetophenone-formaldehyde.
4. The processing aid as claimed in any one of preceding claims, wherein the processing aid is used in the range of 0.2 to 10 phr in halogenated polymer or copolymer for improved rheological properties facilitating better processibility.
5. The processing aid as claimed in any one of preceding claims, wherein the halogenated polymer and copolymer is preferably PVC, PVDC or PVDF.
6. A polyvinyl chloride composition comprising a polyvinyl chloride resin and the processing aid selected from a nitrated aromatic polymer or oligomer or aliphatic or aromatic ketonic resin or combinations thereof along with the other conventional additives for improved rheological properties facilitating better processibility of polyvinyl chloride.
7. The composition as cliamed in claim 6, wherein the nitrated aromatic polymer or oligomer is nitrated polystyrene.
8. The composition as cliamed in claim 6, wherein the aliphatic or aromatic ketonic resin is cyclohexane-formaldehyde or acetophenone-formaldehyde.
9. The composition as claimed in claim 6, wherein the processing aid is used in the range of 0.2 to l0 phr.
10. The compositions as claimed in claim 6, wherein the conventional additives are selected from stearic acid, PE Wax and / or Tin stabiliser.
11. Use of a nitrated aromatic polymer or oligomer or aliphatic or aromatic ketonic resin or combinations thereof as a processing aid for halogenated polymer and copolymer for better processibilty.
Dated this the 6th Day of October 2005
Nitrated polystyrene and / or ketonic resin is disclosed as processing aid for halogenated polymers and copolymers, particularly PVC. Further PVC composition comprising the processing aids like Nitrated polystyrene and / or ketonic resin with improved rheological properties facilitating processibility of PVC is also disclosed herein.
|Indian Patent Application Number||1262/MUM/2005|
|PG Journal Number||26/2010|
|Date of Filing||07-Oct-2005|
|Name of Patentee||MALSHE, VINOD CHINTAMANI|
|Applicant Address||1, Staff Quarters, UDCT Campus, Matunga, Mumbai-400 019|
|PCT International Classification Number||C08F14/08 C08F14/00|
|PCT International Application Number||N/A|
|PCT International Filing date|