JP2001122914A - Method for producing vinyl chloride-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vinyl chloride-based resin capable of providing a molding product suppressing yellowish discoloration in molding and processing by using a complex metal stabilizer such as calcium-zinc mixture, etc., not causing plate out, having slight fish eye resulting from scale, excellent color tone and appearance. SOLUTION: In producing a vinyl chloride-based resin by subjecting a vinyl chloride-based monomer to suspension polymerization in an aqueous medium using a dispersion stabilizer, a β-diketone compound and a polyalkylene oxide are added to the polymerization system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl chloride resin. Specifically, there is little scale generation during polymerization, little plate-out when processing molded articles using composite metal stabilizers such as calcium-zinc compound, less yellowish coloring, less fisheye, color and appearance The present invention relates to a method for producing a vinyl chloride resin capable of giving a molded article having a good quality.

[0002]

2. Description of the Related Art Vinyl chloride resins are used in a wide range of applications from construction materials such as pipes, corrugated sheets and electric wires to food and medical fields such as food wrapping films and medical blood bags. In the above, a composite metal stabilizer such as calcium-zinc, which is more toxic than lead or tin stabilizers generally used in other applications, is preferably used for safety reasons. However, composite metal stabilizers generally have poorer thermal stability than lead or tin-based stabilizers and tend to have yellowish coloring on molded articles. In order to improve such a defect, β having an effect of suppressing coloring is used.
-A method of adding diketone compounds to a vinyl chloride resin has been industrially adopted. Generally, the method is performed by adding a β-diketone compound together with a compounding agent at the time of blending. In addition, there are many known documents, for example, there is an invention (Japanese Patent Application Laid-Open No. 51-11252) on a method of containing a β-diketone compound in a halogen-containing resin. However, in the generally known method of adding β-diketone compounds at the time of blending, β-diketone compounds that are not sufficiently adsorbed on the vinyl chloride resin are complexed with various compounding agents during molding. As a result, plate-out occurs on a die, a screw, or the like, which causes troubles such as streaks or burns on the surface of the molded product, and a small amount of addition causes a problem of insufficient coloring suppression effect.
Therefore, a method has been proposed to solve the above problem by adding the compound during polymerization and dispersing the compound inside the vinyl chloride resin. For example, a method of adding a β-diketone compound during polymerization (JP-A-10-212306), a method of adding a β-diketone compound and a phenolic antioxidant in combination during polymerization (JP-A-6-212908), or A method in which a zinc compound and a β-diketone compound are used in combination and added during polymerization (JP-A-59-8908).
The method of adding β-diketone compounds during polymerization and uniformly dispersing them inside the vinyl chloride resin suppresses yellowing due to deterioration, and plate-out β-diketone compounds as seen by blend addition. Although the effect of solving the problem is extremely effective, simply adding a large amount of β-diketone compounds during the polymerization accelerates the generation of scale, and not only takes a lot of time to remove the scale, but also increases the scale. Serious problems such as an increase in the number of fish eyes in the product, which adversely affect the appearance of the product, arise newly. Therefore, industrially, there is a strong demand for the development of a more excellent method.

[0003]

That is, an object of the present invention is to develop a method for reducing the scale generated by adding a β-diketone compound having an excellent coloring suppressing effect during polymerization, When processing a molded article using a composite metal stabilizer such as a calcium-zinc compound, there is no occurrence of plate-out, less fisheye, yellowish coloring is suppressed, and a molded article having a good color tone and appearance can be provided. An object of the present invention is to provide a method for producing a vinyl chloride-based resin.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, when adding a β-diketone compound to a polymerization system, a polyalkylene oxide was added together. It was found that the scale was reduced by performing the polymerization, and it was found that the desired vinyl chloride resin was obtained, thereby completing the present invention.

That is, the present invention relates to (1) polymerization of a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer in an aqueous medium using a dispersion stabilizer. A method for producing a vinyl chloride resin, characterized in that a β-diketone compound and a polyalkylene oxide are added to the polymerization system when producing the vinyl chloride resin. The method for producing a vinyl chloride resin according to claim 1, wherein the β-diketone compound to be added is stearoylbenzoylmethane (claim 2). 3. The method for producing a vinyl chloride resin according to claim 1 or 2, wherein the method is acetic acid.
(4) The method for producing a vinyl chloride resin according to (1), (2) or (3), wherein the polyalkylene oxide to be added is polyethylene oxide. 5. The method for producing a vinyl chloride resin according to claim 1, wherein 0.001 to 0.5 part by weight is added per 100 parts by weight of the vinyl chloride monomer. And (6) the polyalkylene oxide is added in an amount of 0.0005 to 0.02 parts by weight per 100 parts by weight of the vinyl chloride-based monomer and in a range smaller than that of the dispersion stabilizer. The present invention also relates to a method for producing a vinyl chloride resin according to any one of claims 1, 2, 3, 4 and 5.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The β-diketone compounds used in the present invention mean a general term for compounds having a β-diketone structure in a molecule, and are limited by molecular structures such as a linear structure and a cyclic structure. is not. For example, acetylacetone, benzoylacetone, dibenzoylmethane,
A compound group generally called a β-diketone compound such as stearoylbenzoylmethane can be used, and a compound having three or more ketone groups in a molecule, such as dehydroacetic acid, can also be used.

The β-diketone compounds are preferably added in the range of 0.001 to 0.5 parts by weight per 100 parts by weight of the vinyl chloride monomer. If the added amount is less than 0.001 part by weight, the effect of suppressing coloring may not be sufficient, and if it exceeds 0.5 part by weight, it is difficult to expect an improvement effect commensurate with the added amount. Even within the above addition range, particularly 0.005 to
Addition in the range of 0.1 part by weight is particularly preferable because the balance between the number of added parts and the effect of suppressing coloring is excellent.

When the β-diketone compound is present in the polymerization system at the time of polymerization, the timing of addition and the method of addition are not particularly limited. However, the β-diketone compound is added when the polymerization raw materials such as vinyl chloride monomers are charged. This is preferable because the resin is more uniformly dispersed in the resin.

[0009] The polyalkylene oxide used in the present invention means a polymer compound obtained by polymerizing an alkylene oxide. Examples of such an alkylene oxide include polyethylene oxide, polypropylene oxide, a random copolymer or block copolymer of polyethylene oxide and polypropylene oxide, and the like. Among them, polyethylene oxide is preferable, and polyethylene oxide having a molecular weight of 100,000 to 10,000,000 is suitably used for preventing scale caused by addition during polymerization of β-diketone. Further, among these, polyethylene oxide having a molecular weight of 1,000,000 to 5,000,000 is particularly preferable.

The polyalkylene oxide is used in an amount of 0.0005 to 0.0 per 100 parts by weight of the vinyl chloride monomer.
It is preferred to add in the range of 2 parts by weight. If the number of added parts is less than 0.0005 parts by weight, the effect of reducing the scale may be insufficient, and if it exceeds 0.02 parts by weight, the effect of the dispersion stabilizer on the suspension / dispersion system increases,
Problems such as a decrease in polymerization stability may occur.
Also, when the polyalkylene oxide is added in a larger amount than the dispersion stabilizer, the influence of the polyalkylene oxide on the suspension dispersion system by the dispersion stabilizer becomes large, and the same disadvantages as described above occur.

It is desirable to add the polyalkylene oxide before or simultaneously with the addition of the β-diketone compound in the polymerization system. Like the β-diketone compound, the polyalkylene oxide is added when the polymerization raw materials such as vinyl chloride monomers are charged. Is preferred.

The vinyl chloride monomer in the present invention is, for example, a vinyl chloride monomer alone or a mixture of a copolymerizable monomer mainly composed of the vinyl chloride monomer. Examples of monomers copolymerizable with a vinyl chloride monomer include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-olefins such as ethylene and propylene, methyl acrylate, and methacrylic acid. Examples thereof include alkyl (meth) acrylates such as methyl acrylate, and vinylidene compounds such as vinylidene chloride.

The dispersion stabilizer in the present invention includes, for example, cellulose derivatives such as partially saponified polyvinyl acetate and hydroxypropylmethylcellulose; natural or synthetic high molecular compounds such as gelatin and polyvinylpyrrolidone; nonionic emulsifiers such as sorbitan esters; lauryl sulfate Anionic emulsifiers such as sodium can be used alone or in combination of two or more. Among them, particularly, in combination with the above-mentioned polyalkylene oxide, a combination of partially saponified polyvinyl acetate and polyethylene oxide, and a combination of hydroxypropylmethylcellulose and polyethylene oxide are preferable in terms of polymerization stability and scale prevention effect.

According to the present invention, except for adding a β-diketone compound and a polyalkylene oxide to a polymerization system, a polymerization method using a known vinyl chloride monomer in an aqueous medium is used. , And is not particularly limited. For example, in a polymerization vessel, an aqueous suspension dispersion containing a monomer and an oil-soluble initiator is prepared using a dispersion stabilizer, and polymerization is started by raising the temperature of the dispersion. The target resin can be obtained by collecting the reactive monomer and subjecting the obtained resin slurry to dehydration drying and the like. Examples of the oil-soluble initiator include di (2-ethylhexyl) peroxydicarbonate, tert-butyl peroxypivalate, and tert.
Organic peroxides such as -butyl peroxy neodecanoate, 3,5,5-trimethylhexanoyl peroxide,
Azo compounds such as azobis (isobutyronitrile) and azobis (dimethylvaleronitrile) can be used alone or in combination of two or more. Further, in the present invention, if necessary, a polymerization regulator, a chain transfer agent, an antioxidant, a cross-linking agent, used for polymerization of a vinyl chloride monomer,
A pH adjusting agent, a scale adhesion preventing agent, a gelling improving agent, an antistatic agent, a filler, a buffering agent and the like can be used alone or in combination of two or more.

[0015]

EXAMPLES Hereinafter, specific examples of the present invention will be described in detail, but the present invention is not limited to the following examples. (Example 1) A 3% by weight aqueous solution of partially saponified polyvinyl acetate having an average degree of polymerization of 2000 and a saponification degree of 80 mol% as a dispersion stabilizer was placed in a stainless steel polymerization vessel equipped with a stirrer and a jacket having an internal volume of 1500 liters. Was converted to 0.06 parts by weight in terms of polyvinyl acetate (vinyl chloride monomer 1).
And ter as an oil-soluble initiator.
0.015 parts by weight of t-butyl peroxy neodecanoate (same as above) and 0.02 parts by weight of 3,5,5-trimethylhexanoyl peroxide (same as above) were charged.
0.01 parts of stearoylbenzoylmethane (same as above)
0.5 of polyethylene oxide having an average molecular weight of 4.5 million
The weight% aqueous solution was simultaneously charged with 0.002 parts (the same) in terms of polyethylene oxide weight. After the charging, the pressure inside the polymerization reactor was reduced by a vacuum pump to remove oxygen. Subsequently, 500 kg of a vinyl chloride monomer was charged, and further degassed to 60 kg.
120 parts (the same) of deionized water warmed to ° C was charged. The temperature of the system was raised to 64 ° C. to start polymerization, and subsequently polymerization was carried out at a constant temperature. When the polymerization addition rate reaches 75%,
Unreacted vinyl chloride monomer is collected outside the system to terminate the reaction, and after removing the vinyl chloride monomer in the polymerization vessel to atmospheric pressure, the vinyl chloride resin slurry in the polymerization vessel is discharged to the mixing tank. The resultant was sequentially dehydrated with a dehydrator using centrifugal separation, and subsequently dried in a fluidized drier to obtain a vinyl chloride resin. The obtained resin was blended according to the composition shown in Table 1 and then subjected to a temperature of 17
The mixture was kneaded with a roll having a rotation speed of 20 rpm at 0 ° C. for 3 minutes to prepare a roll sheet having a thickness of 0.7 mm. Using this roll sheet, at a temperature of 170 ° C. and a pressure of 30 kg / c
The plate was pressed under the condition of m ² for 15 minutes to prepare a 5 mm-thick press plate, and the b value indicating the degree of yellowing of the press plate was measured by a color difference meter (# 80 color measuring system manufactured by Nippon Denshoku Industries Co., Ltd.). . Table 2 shows the results. Also,
The mixture obtained by blending with the composition shown in Table 1 was subjected to a cylinder temperature of 1 using a 40 mm single screw extruder equipped with a pipe die.
Extrusion molding was performed under the conditions of 60 ° C., a die temperature of 165 ° C., and 35 rpm, and air was blown into the parison discharged from the die while it was hot to obtain a thinly expanded Fusen-like molded product. The amount of fish eyes contained in 10 g of the film-like portion of the Fusen-like molded product was counted. The results are shown in Table 2. Furthermore, the inside of the polymerization machine after the polymerization was completed was observed, and the degree of scale generation was comprehensively judged from the time required for visual observation and cleaning and the scale weight obtained by cleaning to rank. Table 2 shows the results.
Shown in The degree of plate-out was ranked by visually judging the state of deposits on the roll surface after the roll evaluation and the deposits on the die and screw after the extrusion evaluation. The results are shown in Table 2.

[0016]

[Table 1] (Example 2) The same operation as in Example 1 was carried out except that the amount of stearoylbenzoylmethane added to the polymerization vessel was changed to 0.05 part by weight based on 100 parts by weight of the vinyl chloride monomer. Table 2 shows the results.

Example 3 The above example was repeated except that 0.01 parts by weight of dehydroacetic acid was added to 100 parts by weight of the vinyl chloride monomer instead of adding stearoylbenzoylmethane to the polymerization vessel. Performed similarly to 1. Table 2 shows the results.

Example 4 The above example was repeated except that 0.05 parts by weight of dehydroacetic acid was added to 100 parts by weight of the vinyl chloride monomer instead of adding stearoylbenzoylmethane to the polymerization vessel. Performed similarly to 1. Table 2 shows the results.

Comparative Example 1 The procedure was the same as in Example 1 except that stearoylbenzoylmethane was not added in the polymerization vessel. Table 2 shows the results.

(Comparative Example 2) The same procedure as in Example 1 was carried out except that polyethylene oxide was not added into the polymerization vessel. Table 2 shows the results.

Comparative Example 3 Same as Example 1 except that stearoylbenzoylmethane added to the polymerization vessel was changed to 0.05 part with respect to 100 parts by weight of the vinyl chloride monomer, and polyethylene oxide was not added. I went to. Table 2 shows the results.

Comparative Example 4 Instead of adding stearoylbenzoylmethane to a polymerization vessel, 0.05 parts by weight of dehydroacetic acid was added to 100 parts by weight of vinyl chloride monomer, and polyethylene oxide was not added. The procedure was performed in the same manner as in Example 1 except for the above. Table 2 shows the results.

(Comparative Example 5) To the dry resin obtained in Comparative Example 1 to which no stearoylbenzoylmethane was added at the time of polymerization, 0.01 part by weight of stearoylbenzoylmethane was added at the time of blending with respect to 100 parts by weight of the dry resin. hand,
The procedure was performed in the same manner as in Comparative Example 1 except that the roll evaluation and the extrusion evaluation were performed. Table 2 shows the results.

Comparative Example 6 The same procedure as in Comparative Example 4 was carried out except that stearoylbenzoylmethane added at the time of blending was changed to 0.05 part by weight based on 100 parts by weight of the dry resin. Table 2 shows the results.

[0025]

[Table 2] (Results of Evaluation) From the results shown in the table, the following points can be observed.

(1) In Examples 1 to 4 and Comparative Examples 2 to 4 in which β-diketone compounds were added during polymerization, and in Comparative Examples 4 and 5 added during blending, no β-diketone compounds were added at all. The b value indicating the degree of yellowing of the press plate is lower than that of Comparative Example 1 in which no press is performed, and it is understood that the β-diketone compounds have a coloring suppressing effect. Further, the coloring suppression effect is correlated with the number of added parts of the β-diketone compound.

(2) Comparative Examples 2 to 4 in which β-diketone compounds were simply added during polymerization were compared with Examples 1 to 4 in which β-diketone compounds were added during polymerization in combination with polyalkylene oxide. After the polymerization was completed, a large amount of scale adhered to the inside of the polymerization vessel.
4 shows that the amount of fish eyes was larger than that of Examples 1 to 5.

(3) Comparative Examples 5 and 6 in which the β-diketone compound was added during the blending were compared with Examples 1 to 5 in which the β-diketone compound was added during the polymerization, and the roll surface during the forming process was It can be seen that the plate-out to the screw and the screw appears remarkably.

(4) Examples 1 to 3 in which β-diketone compounds were added in combination with polyalkylene oxide during polymerization
In No. 5, Comparative Example 1 in which the β-diketone compound was not added, Comparative Examples 2 to 4 in which the β-diketone compound was simply added during the polymerization without using the polyalkylene oxide in combination, Comparative Example 4 in which the β-diketone compound was added during the blending, and Compared with Comparative Example 5, plate-out during molding was less, yellowish coloring was suppressed,
It can be seen that a resin with less fish eyes can be obtained.

[0030]

According to the present invention, it is possible to efficiently use a vinyl chloride resin with less plate-out and less yellowish coloring and less fish-eye when molding in a compounded metal stabilizer such as a compounded calcium-zinc compound. Can get well. By producing a molded body using such a resin, a product having good color tone appearance can be obtained.

Claims (6)

[Claims] 1. A vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer is polymerized in an aqueous medium using a dispersion stabilizer to form a vinyl chloride resin. A process for producing a vinyl chloride-based resin, which comprises adding a β-diketone compound and a polyalkylene oxide to a polymerization system during production. 2. The process for producing a vinyl chloride resin according to claim 1, wherein the β-diketone compound to be added is stearoylbenzoylmethane. 3. The process for producing a vinyl chloride resin according to claim 1, wherein the β-diketone compound to be added is dehydroacetic acid. 4. The polyalkylene oxide to be added,
4. The method for producing a vinyl chloride resin according to claim 1, wherein the resin is polyethylene oxide. 5. The chloride according to claim 1, 2, 3 or 4, wherein the β-diketone compound is added in an amount of 0.001 to 0.5 part by weight per 100 parts by weight of the vinyl chloride monomer. A method for producing a vinyl resin. 6. The polyalkylene oxide is used in an amount of 0.0005 to 0.02 per 100 parts by weight of the vinyl chloride monomer.
6. The composition according to claim 1, wherein the compound is added in a range of parts by weight and in a range smaller than that of the dispersion stabilizer.
The method for producing the vinyl chloride resin according to the above.