JP2007119764A - Method for production of vinyl chloride polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vinyl chloride polymer with good formability and holding the physical properties of the produced vinyl chloride polymer by suppressing degradation of the vinyl chloride polymer and suppressing heat decomposition of the vinyl chloride polymer. <P>SOLUTION: The invention relates to the method for producing the vinyl chloride polymer by carrying out an aqueous suspension polymerization of the vinyl chloride or a monomer mixture substantially comprising the vinyl chloride, wherein a thermal stabilizer and a lubricant are added in the aqueous suspension polymerization. An effective result is obtained by adding the thermal stabilizer and the lubricant as a dispersion using a dispersing agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a vinyl chloride polymer.

  Vinyl chloride-based resin molded products are used in a wide range of applications such as construction materials and civil engineering materials such as pipes, corrugated sheets, and electric wires, food wrapping films, medical blood packs, and other food and medical fields.

  This vinyl chloride resin molded product is obtained by molding a vinyl chloride resin, which is a resin mixture obtained by adding additives such as a plasticizer, a heat stabilizer, and a lubricant to a vinyl chloride polymer. A vinyl chloride polymer is produced by suspension polymerization of a monomer mixture containing as a main component in water, and then a plasticizer, a heat stabilizer, a lubricant, etc. are added to the vinyl chloride polymer. It is obtained by adding a product and then molding.

  As such heat stabilizers, lead-based stabilizers, tin-based stabilizers, calcium-zinc-based stabilizers and the like are known (see Patent Document 1), and as lubricants, hydrocarbon-based stabilizers are known. Lubricants and the like are known (see Patent Document 2).

JP 2001-122914 A JP 2003-2913 A

  By the way, as described above, the vinyl chloride resin molded body can be obtained by adding an additive such as a plasticizer, a heat stabilizer, and a lubricant to the vinyl chloride polymer and molding it while heating. Since the vinyl polymer is provided as particles, the heat stabilizer may not easily penetrate into the inside of the particles even if a heat stabilizer is added. For this reason, when it heats, there exists a possibility that thermal decomposition may arise inside the vinyl chloride polymer particle, and it may be colored, and it was difficult to heat it too much.

  In addition, when molding using vinyl chloride polymer particles, the hierarchical particle structure of the vinyl chloride polymer particles is destroyed by shearing force due to contact with the metal surface of a heated molding machine, and melt-kneaded sufficiently. There is a need to. By adding a lubricant to the hierarchical particle structure, peeling can be facilitated due to the slipperiness with the metal surface, but the lubricant is added before the molding process of the vinyl chloride polymer particles. However, the lubricant does not necessarily penetrate into the inside of the particles. For this reason, the slipperiness with the metal surface is not sufficient, sticking, burning, etc. may occur, and molding defects may occur.

  Therefore, an object of the present invention is to suppress thermal decomposition of the vinyl chloride polymer and to improve moldability.

  The present invention solves the above problems by adding a heat stabilizer and a lubricant when aqueous suspension polymerization of a vinyl chloride monomer is performed.

  According to this invention, since the heat stabilizer and the lubricant are added during the polymerization, the heat stabilizer and the lubricant can be contained in the obtained vinyl chloride polymer. For this reason, even when heated during molding, the thermal stabilizer present inside suppresses the thermal decomposition inside the vinyl chloride polymer, and the lubricant present inside peels off due to the lubricity with the metal surface. It is easy, sticking hardly occurs, and thermal decomposition can be suppressed.

The present invention will be described in detail below.
This invention is a method for producing a vinyl chloride polymer by aqueous suspension polymerization of a vinyl chloride monomer, and is characterized by adding a heat stabilizer and a lubricant during the aqueous suspension polymerization. It is a method to do.

  The vinyl chloride monomer refers to a vinyl chloride monomer alone or a monomer mixture obtained by mixing a vinyl chloride monomer as a main component and a copolymerizable monomer. The vinyl chloride polymer refers to a polymer of the vinyl chloride monomer, that is, a vinyl chloride homopolymer or a vinyl chloride copolymer. In addition, said main component means that the content rate of the vinyl chloride monomer in a monomer mixture is the largest.

  As the monomer copolymerizable with vinyl chloride, those conventionally used in the polymerization of vinyl chloride monomers can be used and are not particularly limited. Examples of this copolymerizable monomer include vinyl esters such as vinyl acetate, vinyl propionate and vinyl stearate, α-olefins such as ethylene and propylene, and (meth) methyl (meth) acrylate. Examples thereof include alkyl ethers of acrylic acid, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, octyl vinyl ether, and lauryl vinyl ether, and vinylidene halides such as vinylidene chloride. These can be used alone or in combination of two or more. In the present specification, “(meth) acryl” means “acryl or methacryl”.

  The above aqueous suspension polymerization refers to a polymerization method in which a monomer is dispersed in an aqueous medium such as water with a dispersant and the like and polymerized using a polymerization initiator or the like.

  The polymerization initiator is not particularly limited, but as an oil-soluble polymerization initiator, benzoyl peroxide, lauroyl peroxide, t-butyl peroxypivalate, di (2-ethylhexyl) peroxydicarbonate, diisopropyl peroxy Examples thereof include organic peroxides such as dicarbonate, t-butylperoxyneodecanoate and α-cumylperoxyneodecanoate, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. These polymerization initiators can be used alone or in combination of two or more.

  Examples of the dispersant include, but are not limited to, water-soluble partially saponified polyvinyl acetate (so-called polyvinyl alcohol), water-soluble cellulose derivatives such as hydroxyisopropylmethylcellulose, and the like. The above can be used. In addition to these dispersants, oil-soluble partially saponified polyvinyl acetate, gelatins, nonionic surfactants, anionic surfactants and the like can be mentioned. These can use 1 type, or 2 or more types.

  In the above aqueous suspension polymerization, various kinds of chain transfer agents, antioxidants, crosslinking agents, pH adjusting agents, scale adhesion preventing agents, etc., which are used for the polymerization of ordinary vinyl chloride monomers as required. A polymerization aid can be appropriately used.

  Furthermore, a method for charging a vinyl chloride monomer, a method for applying a scale adhesion inhibitor, a method for stopping polymerization, a method for removing residual vinyl chloride monomer from a vinyl chloride polymer, and a produced vinyl chloride For the method of separating and drying the polymer from the aqueous medium, the method employed in the usual suspension polymerization method of vinyl chloride monomers can be applied.

  As an example of the above-mentioned method of charging the vinyl chloride monomer, in addition to the method of charging all of the vinyl chloride monomer at the initial charging, a part of the vinyl chloride monomer is charged at the initial charging. It is possible to employ a method in which the remaining part of the vinyl chloride monomer is additionally charged in the middle of the charging and aqueous suspension polymerization.

  Furthermore, the shape of the stirring device such as the stirring blade and baffle of the polymerization apparatus used for the aqueous suspension polymerization is not particularly limited, and the former includes a turbine blade, a fan turbine blade, a Faudler blade, And the blue margin. Examples of the latter include a plate type, a cylindrical type, a D type, a loop type, and a finger type.

  The average degree of polymerization of the vinyl chloride polymer constituting the vinyl chloride resin is not particularly limited, but is preferably 500 or more and less than 1500, and more preferably 600 or more and 1400 or less. If it is less than 500, the viscosity tends to be low and the tackiness tends to increase. On the other hand, if it is larger than 1500, there is a tendency for heat generation due to shearing to increase. Examples of a method for obtaining this average degree of polymerization include a method for controlling the polymerization temperature.

  In the aqueous suspension polymerization, it is essential to add a heat stabilizer and a lubricant. Examples of the heat stabilizer include hydrotalcite compounds, epoxy compounds, phosphites, polyhydric alcohols, keto compounds, lead stabilizers, organic tin stabilizers, metal soap stabilizers, and the like.

  Examples of the hydrotalcite compound include synthetic hydrotalcite and natural hydrotalcite. Examples of the epoxy compound include epoxy resin, epoxidized linseed oil, and epoxidized soybean oil. Furthermore, examples of the phosphite include polyphosphite, triphenyl phosphite, and trinonylphenyl phosphite. Furthermore, examples of the polyhydric alcohol include sorbitol, trimethylolpropane, and pentaerythritol. Examples of the keto compound include acetoacetate ester, dehydroacetic acid, β-diketone and the like.

  Examples of the lead stabilizer include lead stearate, dibasic lead phosphite, and tribasic lead sulfate. Examples of the organotin stabilizer include dimethyltin mercapto, dibutyltin mercapto, dioctyltin mercapto, dibutyltin malate, dibutyltin malate polymer, dioctyltin malate, dioctyltin malate polymer, dibutyltin laurate, dibutyltin laurate Examples thereof include polymers. Furthermore, examples of the metal soap stabilizer include calcium-zinc stabilizer, barium-zinc stabilizer, barium-cadmium stabilizer and the like. These heat stabilizers may be used alone or in combination of two or more.

  Among these, it is more preferable to use the hydrotalcite compound because the effects of the present invention are more effectively exhibited and from the viewpoint of toxicity and the like.

  The addition amount of the heat stabilizer is preferably 50 ppm or more and 5000 ppm or less, and preferably 100 ppm or more and 3000 ppm or less with respect to the total charge of the monomer mixture containing vinyl chloride or vinyl chloride as a main component. If it is less than 50 ppm, the effect of adding a heat stabilizer cannot be exhibited. On the other hand, if it exceeds 5000 ppm, the polymerization stability is inhibited and the particles are coarsened, so that it tends to be difficult to obtain vinyl chloride polymer particles having the desired quality.

  Examples of the lubricant include polyethylene wax, paraffin wax, montanic acid wax, fatty acid such as stearic acid, fatty alcohol such as stearyl alcohol, alcohol ester of fatty acid such as butyl stearate, polyglycol ester of fatty acid, polyhydric alcohol, Examples thereof include polyglycol and polyglycerol. These may be used alone or in combination of two or more.

  The addition amount of the lubricant is preferably 100 ppm or more and less than 5000 ppm, and preferably 200 ppm or more and 3000 ppm or less with respect to the total amount of the vinyl chloride or the monomer mixture mainly composed of vinyl chloride. If it is less than 100 ppm, the effect of adding a lubricant cannot be exhibited. On the other hand, when it is 5000 ppm or more, polymerization stability is hindered and the particles are coarsened, so that it is difficult to obtain vinyl chloride polymer particles having a desired quality.

  As a method for adding the heat stabilizer or the lubricant, it may be added in the form of powder or may be added as a dispersion finely dispersed in an aqueous medium. In particular, when at least one of the heat stabilizer and the lubricant is added as a dispersion, the dispersibility of the heat stabilizer and the lubricant is improved during the polymerization. Therefore, the heat stabilizer and the lubricant in the resulting vinyl chloride polymer are improved. Therefore, the thermal decomposition during the subsequent molding process can be more efficiently suppressed, and the slipperiness during the subsequent molding process can be made more uniform.

  Examples of the aqueous medium include water and a mixed solvent of water and a water-soluble alcohol such as methanol or ethanol.

  The dispersion preferably contains a dispersant for dispersing the heat stabilizer and the lubricant. As the dispersant, if the dispersant used for the polymerization of vinyl chloride is used, it can be used as a dispersant for the polymerization of vinyl chloride, which is efficient. In this case, the entire amount of the dispersant used for the polymerization of vinyl chloride may be used as a dispersant for these heat stabilizers or lubricants, or a part thereof may be used. From the viewpoint of the addition efficiency, it is preferable to use the entire amount.

  As the dispersant, among the above descriptions, water-soluble partially saponified polyvinyl acetate, oil-soluble partially saponified polyvinyl acetate, and water-soluble cellulose derivatives are preferable. The water-soluble partially saponified polyvinyl acetate preferably has a saponification degree of 60 to 100% and an average polymerization degree of 500 to 3000. A saponification degree of 30 to 55% and an average polymerization degree of 100 to 1000 are more preferred.

  When using a heat stabilizer or a lubricant having a low affinity for water, when dispersed using oil-soluble partially saponified polyvinyl acetate as the dispersant, in the vinyl chloride polymer particles after polymerization, Since the heat stabilizer and the lubricant are more uniformly dispersed, the dispersibility is improved, which is more preferable.

  The vinyl chloride polymer obtained by the above method contains a thermal stabilizer and a lubricant up to the inside of the particles made of this vinyl chloride polymer, and therefore, decomposition is caused by heating during molding using this. While being able to suppress effectively, it can suppress that a resin adheres to a metal surface in the process of gelation or a molten state, and can improve moldability.

  In particular, when the method of the present invention in which a heat stabilizer and a lubricant are added in the production process of the above vinyl chloride polymer is used, the heat stabilizer and the lubricant are more than the case where both of them are added only in the conventional molding process. The same effect can be obtained by reducing the amount of added as a whole.

  Next, a method for molding using the vinyl chloride polymer obtained by the above method will be described. First, a heat stabilizer, a lubricant, and, if necessary, a plasticizer, a modifier, a filler and the like are added to the vinyl chloride polymer to obtain a vinyl chloride resin composition. Next, this vinyl chloride resin composition is molded by subjecting it to extrusion molding, injection molding, calendar molding, press molding or the like, and a molded body can be obtained.

  Examples of the plasticizer include dibutyl phthalate, di-2-ethylhexyl phthalate, di-2-ethylhexyl adipate, and the like. Examples of the modifier include MBS (methyl methacrylate / butadiene / styrene resin), ABS (acrylonitrile / butanediene / styrene resin), chlorinated polyethylene, acrylic polymer, EVA (ethylene / vinyl acetate resin), PMMA (polyethylene). Examples thereof include methyl methacrylate) and NBR (nitrile butylene rubber). Furthermore, examples of the filler include calcium carbonate, clay, and talc. These may be used alone or in combination of two or more.

  In this molding process, the effects of the heat stabilizer and the lubricant can be more accurately exhibited by adding the heat stabilizer and the lubricant. As the heat stabilizer and lubricant used at this time, the same ones as described above can be used. Further, the same heat stabilizer or lubricant used in the production process of the vinyl chloride polymer may be used, or a different one may be used. Among them, it is more preferable to use the hydrotalcite compound at the time of aqueous suspension polymerization and to use a metal soap stabilizer, particularly a calcium-zinc stabilizer (calcium stearate-zinc stearate) at the time of molding. .

  Conventionally, when molding processing is performed using vinyl chloride polymer particles, a heat stabilizer, a lubricant, or the like is added, and at that time, so-called hot blending that is heated to about 110 ° C. may be performed. At this time, since lead stearate generally used as a lead-based stabilizer is in a molten state, it is easily impregnated inside the vinyl chloride polymer particles. Further, since the organic tin stabilizer is in a liquid state, it is easily impregnated inside the vinyl chloride polymer particles. On the other hand, metal soap stabilizers, particularly calcium-zinc stabilizers generally used (calcium stearate-zinc stearate) have a high melting point of 120 ° C. or higher. However, it is difficult to impregnate the inside of the vinyl chloride polymer particles. For this reason, the use of the hydrotalcite compound in the method of the present invention, that is, in the aqueous suspension polymerization, makes it difficult to impregnate the inside of the vinyl chloride polymer particles during blending, particularly calcium-zinc. The effect can be exhibited even when the system stabilizer is added and blended during molding.

  As mentioned above, when heat stabilizers and lubricants are added in both the vinyl chloride polymer production process and the molding process, the amount of heat stabilizers and lubricants added is higher than when these are added only in the conventional molding process. As a whole, the same effect can be obtained.

  In the above-described molding process, in addition to the above-mentioned additives, a stabilizing aid, a modifier, a processing aid, an antioxidant, a light stabilizer, a pigment, a filler, and the like are added as necessary. Also good.

  Hereinafter, the present invention will be specifically described by way of examples. First, physical properties and evaluation methods in the following Examples and Comparative Examples, and raw materials used are described.

[Evaluation of the physical properties]
(Average polymerization degree)
200 mg of a vinyl chloride polymer is dissolved in 50 ml of nitrobenzene, and the resulting solution is put into an Ubbelohde viscometer held in a constant temperature water bath at 30 ° C., and the number of seconds falling between the marked lines is measured. I asked for a degree.

(Dynamic pyrolysis)
100 parts by weight of the obtained vinyl chloride polymer 0.8 parts by weight of calcium stearate, 0.4 parts by weight of zinc stearate, 2 parts by weight of epoxidized soybean oil, 0.5-phosphorus chelator (Mark 1500, manufactured by Asahi Denka Kogyo) After the resin composition was prepared by mixing parts by weight, 59 g of this resin composition was filled in R60 Plast Mill (Toyo Seiki Seisakusho Co., Ltd .: 30C150) R60 and kneaded at a temperature of 170 ° C. and a rotation speed of 40 rpm. The time until the resin composition was thermally decomposed and the torque began to increase was measured.

(Oven pyrolysis)
The resin composition used for evaluation of dynamic thermal decomposability was kneaded on a 150 ° C. roll for 5 minutes, and then taken out as a sheet having a thickness of 0.75 mm. This roll sheet was placed in an oven at 190 ° C., and the time until the sheet was thermally decomposed and blackened was measured.

[raw materials]
(Polymerization initiator)
・ Tert-Butylperoxyneodecanoate

(Dispersant)
Dispersant 1: partially saponified polyvinyl acetate (saponification degree 89 mol%, polymerization degree 2300)
Dispersant 2 ... partially saponified polyvinyl acetate (saponification degree 71 mol%, polymerization degree 700)

(Heat stabilizer)
・ Hydrotalcite: manufactured by Kyowa Chemical Industry Co., Ltd .: Algamizer

(Lubricant)
Fatty acid polyol ester: manufactured by Cognis: Loxiol G15, hereinafter abbreviated as “G15”.
-Hydroxy stearic acid: Cognis Co .: Loxiol G21, hereinafter abbreviated as "G21".

(Examples 1-2, Comparative Examples 1-3)
The stainless steel polymerization can with a stirrer and jacket with an internal volume of 400 liters was charged with the charge 1 shown in Table 1, and deaerated with a vacuum pump. Next, Charge 2 was charged as a dispersant. Thereafter, Charge 3 was charged, warm water was circulated through the polymerization can jacket, and the temperature was raised to 56.5 ° C. to initiate polymerization. In Example 2, when the polymerization conversion rate reached 50%, an amount of vinyl chloride monomer shown in Table 1 was additionally charged at an addition rate of 22 kg / hr.
When the internal pressure of the polymerization can decreased by 0.15 MPa from the saturated vapor pressure of the vinyl chloride monomer at 56.5 ° C., the unreacted monomer was recovered and the polymerization was terminated.
Said evaluation was performed about the particle | grains of the obtained vinyl chloride type polymer. The results are shown in Table 1.

(Comparative Example 4)
To a part of the vinyl chloride polymer particles obtained in Comparative Example 1, the heat stabilizers and lubricants in the amounts shown in Table 1 were added. Said evaluation was performed about the obtained particle | grains. The results are shown in Table 1.

(Example 3)
Hydrotalcite, G15 and G21 were previously mixed with Dispersant 1 and Dispersant 2 to prepare an aqueous dispersion (the blending ratio is the same as in Example 1).
About the vinyl chloride polymer particles obtained by carrying out the polymerization of the vinyl chloride monomer in the same manner as in Example 1 except that the whole amount was used as the charge 2 and the charge 1 was not used. Evaluation was performed. The results are shown in Table 1.

(As a result of evaluation)
The following points are observed from the results shown in Table 1.
(1) The dynamic thermal decomposability of Example 1 in which a heat stabilizer and a lubricant were added at the time of polymerization was better than Comparative Example 2 in which only the heat stabilizer was polymerized and Comparative Example 3 in which only the lubricant was polymerized, and The inventors have found that the addition of both components in combination has a greater improvement range and a synergistic effect than the improvement of thermal decomposability by itself. Moreover, it turns out that the effect of Example 1 is larger than the comparative example 4 which added both components at the time of a blend. A similar effect was confirmed with oven pyrolysis. From these, a heat stabilizer and a lubricant are polymerized and added, and finely dispersed in a vinyl chloride polymer, thereby suppressing the sticking of the resin composition to the metal surface of the molding machine and expressing the lubricity more uniformly. Therefore, it is considered that the thermal stabilizer that suppresses shearing and finely disperses the decomposed hydrochloric acid gas can be captured in the very initial stage, so that the initial thermal deterioration is suppressed and a synergistic effect is exhibited.

(2) In Example 2, the thermal stability is further improved by adding the vinyl chloride monomer during the polymerization, compared to Example 1 in which the additional charging is not performed. This is because the vinyl chloride monomer is present on the surface of the vinyl chloride polymer particles by post-adding the vinyl chloride monomer at the end of the polymerization, and as a result, a heat stabilizer or lubricant that is finely dispersed in the particles. Are considered to be finely dispersed on the center side of the particles. For this reason, it is considered that the heat stability effect and the slipperiness are not consumed in the early stage of molding, and the effect is exhibited in the later stage of molding when the particles are destroyed.

(3) In Example 3, a heat stabilizer and a lubricant are dispersed in a dispersion. By using this, it is considered that the heat stabilizer and the lubricant were more uniformly dispersed, and thereby the effects of the above (1) and (2) could be further synergistically exhibited.

Claims (9)

In a method for producing a vinyl chloride polymer by aqueous suspension polymerization of a vinyl chloride monomer comprising a vinyl chloride monomer or a monomer mixture mainly composed of a vinyl chloride monomer,
A method for producing a vinyl chloride polymer, comprising adding a heat stabilizer and a lubricant during the aqueous suspension polymerization.   The method for producing a vinyl chloride polymer according to claim 1, wherein the addition amount of the lubricant is 100 ppm or more and less than 5000 ppm with respect to the total amount of the vinyl chloride monomer.   The method for producing a vinyl chloride polymer according to claim 1 or 2, wherein the heat stabilizer is a hydrotalcite compound.   The method for producing a vinyl chloride polymer according to any one of claims 1 to 3, wherein at least one of the lubricant and the heat stabilizer is added as a dispersion.   The said dispersion liquid contains a dispersing agent, The manufacturing method of the vinyl chloride polymer of Claim 4 characterized by the above-mentioned.   The method for producing a vinyl chloride polymer according to any one of claims 1 to 5, wherein the vinyl chloride polymer has an average degree of polymerization of 500 or more and less than 1500.   The method for producing a vinyl chloride polymer according to any one of claims 1 to 6, wherein a part of the vinyl chloride monomer is additionally charged during the aqueous suspension polymerization.   A vinyl chloride polymer containing a heat stabilizer and a lubricant.   A heat stabilizer and a lubricant are further added to the vinyl chloride polymer obtained by the method for producing a vinyl chloride polymer according to any one of claims 1 to 7, or the vinyl chloride polymer according to claim 8. Next, a method for producing a vinyl chloride resin molded body, which is molded.