WO1993013145A1

WO1993013145A1 - A polyvinyl chloride ready for processing and its preparation method

Info

Publication number: WO1993013145A1
Application number: PCT/FI1992/000361
Authority: WO
Inventors: Hannu Harjuhahto; Henrik Holmqvist; Esa Karhu; Leif Rockas; Tommy Ånäs
Original assignee: Neste Oy
Priority date: 1991-12-31
Filing date: 1992-12-23
Publication date: 1993-07-08
Also published as: AU3161193A; FI95473B; BR9207004A; FI916191A; SI9200418A; SK78194A3; HUT67926A; CZ154194A3; CA2127103A1; NO942385D0; LTIP255A; EE9400236A; FI95473C; LV10114B; RU94031159A; FI916191A0; EP0619829A1; LV10114A; YU112392A; JPH07506848A

Abstract

The invention relates to a homo- or copolymer composition of a vinyl chloride, which is ready for processing and which contains additives necessary from the point of view of the processing, such as stabilizers, lubricants, colourants, reinforcing agents and processing aids, and to a method for its preparation. The polymer has been prepared by adding into the polymerization reactor in the beginning of the polymerization, during it or at the end thereof 0.01-50 weight-% of the amount of vinyl chloride a liquid olefin oligomer and/or ethylene olefin copolymer or olefin terpolymer.

Description

A polyvinyl chloride ready for processing and its preparation method

The invention relates to a vinyl chloride, which is directly ready for processing, and in which the necessary processing additives, such as stabilizers, lubricants, colourants and reinforcing agents, etc., are added to the polymer in the polymeri¬ zation reactor. The invention also relates to a method for preparing such a vinyl chloride polymer.

Polyvinyl chloride (PVC) is pricewise an economical thermoplastic suitable for a large number of applications. In order to make PVC suitable for processing, one or more stabilizers, lubricants, pigments and/or modifiers are to be added to the resin obtained in the polymerization. From the point of view of the PVC- product manufacturer, it would be desirable that the polymer purchased by him/her would be as ready as possible for processing. Nowadays, this requires the building of a separate mixing plant either after the polymerization reactor or at the plant of the end-product manufacturer. Research work on the addition of additives, especially stabilizers, during the polymerization have been made and some patent publications are available.

In the US patent 3862066 is described a suspension polymerization system of vinyl chloride, in which system various additives, such as stabilizers, lubricants, pigments, etc. are added to a polymerization reactor in the beginning of the polymerization or during the polymerization. At the end of the polymerization, an inhibitor stopping the polymerization is added in order to obtain the desired conversion.

In the patent publication DE 3630318, polyoxazoline of a certain type is used as a suspension stabilizer, whereby organic or inorganic zinc compounds may be added to the polymerization reactor as prestabilizers. The final stabilization is performed subsequently in a conventional manner. In the patent publication GB 1577030, the additives have been introduced into the polymerization reactor in connection with the bulk polymerization of vinyl chloride. According to the publication, conventional additives may be used. The polymerization may also be a two-step polymerization, whereby the additives are added in the second step. E.g. stabilizers, lubricants and processing aids are added to the polymerization.

However, the methods known currently have apparently not been successful in plant scale, as far as it is known, since such processes are commercially not in use, in which a polymer suitable for processing could be obtained from the polymerization. In the experiments leading to the present invention, the addition of the additives of polyvinyl chloride directly into the polymerization reactor were examined according to the above-mentioned publications, but it was then observed that the products were not suitable for use. Waste product, which was lumpy or adhered onto the walls of the reactor, was produced to a very great extent. The wax-like lubricants used in the publications disturbed the forming of the dispersion in the reactor.

In accordance with the invention, it has been observed that the addition of PVC additives into the polymerization is possible, if certain vehicles are simultaneous¬ ly added into the reactor. Thus, the homo- or copolymer composition according to the invention is characterized in that it has been prepared by adding into the polymerization reactor in the beginning of the polymerization, during it or at the end thereof 0.01-50 weight-% of the amount of vinyl chloride a liquid olefin oligomer and/or ethylene olefin copolymer or olefin terpolymer.

The liquid olefin oligomer may be a dimer, trimer, tetramer, pentamer or hexamer of α-olefins or internal olefins (C^-C^_Q) or their mixture, whereby the lengths of the carbon chains are C_2Q-C_10Q. The oligomer may contain double bonds or it may be hydrated.

Optionally, a liquid polymer may be used, which is an elastomeric ethylene propylene polymer, in which e.g. dicyclo pentadiene or ethylidene norbornene is used as the termonomer. The liquid polymer may be used in addition to the oligomer or in place thereof. The selection of the oligomer and/or the liquid polymer to be used depends on the desired end product. The addition of the liquid oligomer and/or polymer into the polymerization reactor thus makes the addition of other additives possible in the beginning of the polymerization or during it, and a polymer ready for processing is obtained as a product.

PVC-polymers ready for processing prepared in the inventive method may be used for the same products as compounds prepared by means of a conventional polymerizing and mixing technique. They may be processed e.g. by extrusion, injection moulding, blow molding or calendering, and various products, such as pipes, pipe fittings, sheets, profiles and bottles may be prepared.

Suitable additives are the same as those used in the preparation of a conven- tional mixture. As stabilizers may be used lead compounds, such as lead sul¬ phate, -phosphite, -carbonate or -phtalate or barium/zinc-, calcium/zinc- or tin compounds. As costabilizers may be used lead-, calcium- or zinc stearates, epoxidized soyabean oils, epoxidized linsead oils or epoxidized fatty-acid esters.

As fillers may be used e.g. calcium carbonates, kaolin, silica or aluminium hydroxide.

Suitable fire-retardant agents are e.g. antimony trioxide, zinc borate, zinc oxide or aluminium hydroxide.

As external lubricants may be used e.g. lead-, calcium- or zinc stearates, fatty acids, fatty-acid esters, -alcohols or -amides, montan acid wax or -esters, paraffin-, hydrocarbon- or polyethylene waxes.

Suitable colourants are carbon black, titanium dioxide, various organic and inorganic pigments.

As a processing aid is suitable e.g. a polymethyl methacrylate and as a reinforc- ing agent various polymers, such as acrylnitrile butadiene styrene (ABS), meth- acrylate butadiene styrene (MBS), chlorinated polyethylene (CPE), ethylene vinyl acetate (EVA) or various acrylate plastics.

The polymerization is performed in a similar method as the conventional PVC preparation by the suspension polymerization method. The vinyl chloride is dispersed in water by using e.g. polyvinyl alcohol (PVA) or cellulose derivatives as a suspending agent. The initiator of the polymerization is an organic peroxide soluble in the monomer. Depending on the product, the polymerization tempera- ture may typically be 50-70°C and correspondingly the pressure 7-12 bar. The polymerization time is most usually 4-8 hours. The length of the polymer chain is nearly totally determined according to the temperature. At the final step of the polymerization reaction, the polymerization pressure starts to decrease. After the pressure has decreased to the desired value, the batch is transferred to a degassing or stripping container, in which the unpolymerized monomer is recovered and returned into the process. After the stripping, the PVC-water mixture is dried, whereby part of the water is mechanically separated, the remainder by means of heat and finally, the product is screened.

The inventive polymerization differs from the conventional polymerization basically because of the fact that the oligomer and/or the liquid polymer as well as the additives normally to be mixed separately after the polymerization are introduced into the polymerization reactor already before the start of the polymerization, during it or after it in one or more steps.

By using in the polymerization of vinyl chloride the inventive method, many advantages are reached in the process compared to the known technique. When the additives are introduced already in the polymerization step, the homogenous distribution of the additives is improved compared to that in the preparation of a conventional mixture, in which the additives are dry-mixed into the polymer before treatment. The additives can be introduced into the polymerization reactor as a water solution or suspension, and thus the dusting problems, which occur during a conventional mixing process, are avoided. The polymerization time decreases, when the degree of polymerization at high conversions increases as a result of a rapid pressure drop and a higher conver¬ sion rate is obtained.

The stripping conditions can be maintained harder in a batch-type stripping equipment, since the heat stabilizers have already been added to the polymer before the stripping. Then, the monomer emissions into the air and waste waters decrease and the raw-material balance is improved. The colouring and the thermal decomposition of the polymer during the stripping are completely avoided.

The economy of the drying step can be improved by using a higher inlet tem¬ perature and a higher temperature difference. The energy consumption decreases because of the improved thermal efficiency. The thermal decomposition during the drying can be avoided even at a temperature exceeding 100°C, since the heat stabilizers have been added already during the polymerization.

The screening step is intensified, since due to the metal-containing additives, the occurrence of static electricity decreases and smaller meshes may be used.

The fluidity of the final polymer is better due to a higher density and a higher granular size. As a result, the dusting problems of the final polymer decrease.

If heavy metals, such as lead, are used for the stabilization, their amount can be decreased ( < weight-%) for a better distribution.

Conventional lubricants are most often not needed, and the need for lubrication essentially decreases, which is especially useful from the point of view of econ¬ omy in connection with extrusion and injection moulding.

The following non-limiting examples are shown for illustrating the invention:

The polymerizations are performed in an autoclave-type polymerization reactor. Standard methods have been used for analyzation: volume weight: ISO R 60, viscosity number and K-value: ISO R 174, and softener absorption (DOP): ISO 4608.

Examples 1-5

Into a polymerization reactor was batched 10 kg of vinyl chloride (VCM) and 15 kg of water. Into the reactor was also added calcium stearate and lead sulphate or zinc stearate for stabilization. A dispersing agent (polyvinyl alcohol) was added in the beginning of the polymerization and during it. In addition to a dicetyl peroxide carbonate initiator, lauryl peroxide was also used. The oligomer was added in the beginning of the polymerization. The oligomer used was a hydrated decene oligomer, which mainly contained tetramer (C^) and to some extent trimer ( ^_Q) and pentamer (C₅₀). The polymerization recipes are shown in Table 1 and the results in Table 2.

Table 1. Polymerization recipe

Amount of chemicals g/kg of vinyl chloride.

Table 2. Polymerization results

Example Conversion Polymerization time Volume weight Granular size Porosity % min g/1 D50, μm %

Into a polymerization reactor was batched 10 kg of vinyl chloride (VCM) and 15 kg of water. Into the reactor was also added calcium stearate and lead sulphate for stabilization. A dispersing agent (PVA) was added in the beginning of the polymerization and during it. In addition to a dicetyl peroxide carbonate initiator, an auxiliary catalyst (cumylperoxy neodecanoate) was also used. The oligomer and/or liquid ethylene propylene polymer (E-P) was added in the beginning of the polymerization. The hydrated oligomer used was a mixture of tetramer (C₄₀) and pentamer (C₅₀) and the liquid polymer in the Examples 6 and 7 an ethylene propylene dicyclopentadiene terpolymer, in Example 8 an ethylene propylene norbornene terpolymer and in Example 9 an ethylene propylene copolymer. The polymerization recipes are shown in Table 3 and the results in Table 4. Table 3. Polymerization recipe

Amount of chemicals g/kg of vinyl chloride.

Table 4. Polymerization results

Example Conversion Polymerization time Volume weight Granular size Porosity % min g/i D50, m %

The plant scale polymerizations have been performed with conventional polymerization reactors by using a technique used in the normal PVC prepara- tion, except that during the polymerization an oligomer of olefin and/or liquid ethylene propylene copolymer as well as other additives have been added. As a reference grade has been used a commercial resin, whose K-value is 68. In the resin analyses and in the testing of pieces made from the resin, standard methods have been used. The additives used are shown in Table 5 and the resin analyses in Table 6.

Table 5. Additives used

Example 10 Example 11 Example 12

Oligomer % 0.8 Ethylene propylene copolymer %

Ca stearate % 1.0

Zn stearate % 0.8 Pb sulphate %

Epoxidized soyabean oil % 3.0

Table 6. Resin analyses

Example 10 Example 11 Example 12 S-116

Volume-weight kg/m³ 498

Plasticizer abs. (DOP) % 24.0

Viscosity number 107.4 K-value 65.6

Particle size D 50, μm 160

Example 13

Pipe extrusions from the resin of Examples 10 and 11:

Pipes (φ 110/3.2 mm) were prepared from the resins with a CM65 2-screw extruder. Conic screws: diameter 65/120 mm, length 1210 mm, operating speed max. 34.4 rpm and total torsion 10.2 kNm.

Falling weight impact tests were performed for the pipes according to the standard SS3064. In this case, the falling weight is 6.0 kg and the drop-weight tip diameter 25 mm. The pipes were kept in a temperature of -10°C or -20°C for 24 hours before the performance of the falling weight test. The reference grade is a PVC resin produced by a conventional method, into which PVC resin the stabilizers have been dry mixed. The results of the falling weight tests are shown in Table 7. It can be observed from the results that the polymer prepared by the method is according to this invention by its impact strength extremely good and that the pipes manufactured therefrom are also very well suitable for cold conditions.

Table 7. Results of falling weight impact tests

Reference Example 10 Example 11

-10°C/24 h 162 cm 185 cm 212 cm

-20°C/24 h 81 cm 194 cm 209 cm

Examples 14-15

A polymerization in the same conditions and by using same additives as described in Example 2 of the US patent 3862066. When the paraffin wax and stearamide used as a lubricant in the Examples of the patent were replaced with an olefin oligomer, which was a mixture of a decene tetramer (C^) and pentamer (C₅₀), a proper polymer was obtained, which was yet fairly coarse, and no waste product occurred. The paraffin wax used according to the US patent did not dissolve, and it disturbed the dispersion. The polymerizations were performed in an autoclave reactor and the amount of the vinyl chloride used was 1.250 kg and the amount of water 1.850 kg. The additives used are shown in Table 8 and the resin analyses in Table 9.

Table 8. Additives g/kg of VC

Table 9. Resin analyses

Examples 16-19

Into the polymerization reactor was added 13 kg of vinyl chloride monomer (VCM), 15.6 kg of water and as dispersing agent totally 1.4 kg of polyvinyl alcohol /kg of VCM. As an initiator was used dicetyl peroxide carbonate 1.3 g /kg VCM. 10 g lead sulphate / kg VCM was added in the begmning of the polymerization. The used oligomer was hydrated decene oligomer containing tetrames ( J_Q), pentamers (C₅₀) and heptamers (Cg_g). Oligomer was added:

Example 16: in the beginning of the polymerization reaction Example 17: during the reaction, 40 min from the beginning Example 18: during the reaction, before the pressure release Example 19: to the slurry, after gas removal

Table 8. Polymerizations and resin analyses

Example 20

Polymerization was performed in the same method as in Example 16, except that the oligomer used was made from internal olefin mixture containing 90% C₁₅ olefin and 10% C₁₆ olefin. The oligomer contained 47% of dimers, 40% trimers and 13% tetramers. The polymerization results were:

Claims

1. A homo- or copolymer composition of a vinyl chloride, which is ready for processing and which contains additives necessary from the point of view of the processing, such as stabilizers, lubricants, colourants, reinforcing agents and processing aids, characterized in that it has been prepared by adding into the polymerization reactor in the beginning of the polymerization, during it or at the end thereof 0.01-50 weight-% of the amount of vinyl chloride a liquid olefin oligomer and/or ethylene olefin copolymer or olefin terpolymer.

2. A polymer according to Claim 1, characterized in that the vinyl chloride polymer has been prepared by means of a suspension polymerization method.

3. A polymer according to Claim 1, characterized in that the ohgomer is prefer- ably a dimer, trimer, tetramer, pentamer or hexamer of a C^Cgg α -olefin or an internal olefin or their mixture.

4. A polymer according to Claim 1, characterized in that the oligomer is most preferably an oligomer of some C₈-C₁₄ α -olefin, wherein the length of the carbon chain is C₁₆-C₁₀₀.

5. A polymer according to Claim 1, characterized in that the liquid olefin polymer is preferably an ethylene propylene copolymer.

6. A polymer according to Claim 1, characterized in that the liquid olefin polymer is preferably an ethylene propylene diene terpolymer.

7. A polymer according to Claim 1, characterized in that the liquid olefin polymer is most preferably an ethylene propylene dicyclopentadiene terpolymer or an ethylene propylene ethylidene norbornene.

8. A method for preparing a homo- or copolymer composition of vinyl chloride, which is ready for processing and which contains additives necessary from the point of view of the processing, such as stabilizers, lubricants, colourants, rein forcing agents and processing aids, characterized in that into the polymerizatio reactor has been added in the beginning of the polymerization, during it or a the end thereof 0.01-50 weight-% of the amount of vinyl chloride a liquid olefi oligomer and/or ethylene olefin copolymer or olefin terpolymer.

9. A method according to Claim 8, characterized in that the oligomer is prefer ably a dimer, trimer, tetramer, pentamer or hexamer of a C₄-C₃₀ α -olefin or a internal olefin or their mixture.

10. A method according to Claim 8 or 9, characterized in that the oligomer i most preferably an oligomer of some C₈-C₁₄ a -olefin, wherein the length of the carbon chain is C₁₆-C₁₀₀.

11. A method according to Claim 8, characterized in that the liquid olefi polymer is preferably an ethylene propylene copolymer.

12. A method according to Claim 8, characterized in that the liquid olefin polymer is preferably an ethylene propylene diene terpolymer.

13. A method according to Claim 8, characterized in that the liquid olefin polymer is most preferably an ethylene propylene dicyclopentadiene terporymer or an ethylene propylene ethylidene norbornene.