JP2001048930A - Production of vinyl chloride-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a vinyl chloride-based resin which can give a molded article that does not have yellow color, is free from the generation of bleedout, scarcely contains fly ashes caused by scales, and has a good color and a good appearance, when molded in the presence of a composite metal stabilizer such as a calcium-zinc compounded stabilizer. SOLUTION: This method for producing a vinyl chloride-based resin comprises polymerizing a vinyl chloride-based monomer in an aqueous medium in a suspension state. Therein, a β-diketone compound such as stearoylbenzoylmethane or dehydroacetic acid is added to the vinyl chloride-based resin at a post- treatment stage after the polymerization.

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, and when processing molded articles using composite metal stabilizers such as calcium-zinc compounds, there is little plate-out, yellowish coloring is suppressed, fisheye is small, and color tone and appearance are good. The present invention relates to a method for producing a vinyl chloride resin capable of providing a molded article.

[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 a diketone compound to a vinyl chloride resin is industrially practiced. That is, a method of adding a β-diketone compound together with a compounding agent at the time of blending is generally carried out, and many known documents are also known. For example, a method in which a β-diketone compound is contained in a halogen-containing resin (Japanese Patent Application Laid-Open No. 51-11252) is disclosed. In addition, some methods of adding the compound at the time of polymerization have been reported. 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 zinc. A method in which a compound and a β-diketone compound are used in combination during polymerization (JP-A-59-8908) and the like are disclosed.

[0003] The method of adding a β-diketone compound to a vinyl chloride resin is extremely effective in suppressing yellowing due to deterioration, but as in the prior patent, the β-diketone compound is added during polymerization. If added in a large amount, there is a serious problem that the polymerization is delayed and the productivity is lowered, the amount of the initiator used has to be increased, and the production cost is increased. Not only takes a lot of time to remove the scale, but also causes serious problems such as an increase in fish eyes in the product due to the scale and adversely affecting the appearance of the product. On the other hand, in the generally known method of adding a β-diketone compound at the time of blending, a β-diketone compound that is not sufficiently adsorbed on a vinyl chloride resin is complexed with various compounding agents during molding processing. There is a problem that plate-out occurs on the die, screw, etc., which causes troubles such as streaks and burns on the molded product surface, and there is a problem that if the added amount is small, the coloring suppression effect becomes insufficient. Industrially, there is a strong demand for the development of better methods.

[0004]

That is, an object of the present invention is to provide a plate-out method for processing a molded article using a composite metal stabilizer such as a calcium-zinc compound without the generation of scale, as in the case of addition during polymerization. It is an object of the present invention to provide a method for producing a vinyl chloride-based resin, which is free from occurrence of yellowish color, has less fish eyes, suppresses yellowish coloring, and can provide a molded article having good color tone and appearance.

[0005]

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on an optimum method of adding a β-diketone compound having a coloring suppressing effect to a vinyl chloride resin. By adding an appropriate amount of the β-diketone compound to the resin during the post-treatment stage after the polymerization, not during the polymerization,
It is possible to avoid the problems of retarding the polymerization and promoting the scale of the β-diketone compounds, which are problems, and to further reduce plate-out during molding as compared with the addition of the blend. It was completed.

That is, the present invention provides (1) suspension polymerization of a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer in an aqueous medium, In the production of resin, β
-A method for producing a vinyl chloride resin characterized by adding a diketone compound (claim 1); (2) adding β-
The method for producing a vinyl chloride resin according to claim 1, wherein the diketone compounds are β-diketone compounds. (3) β-diketone compounds to be added,
3. The method for producing a vinyl chloride resin according to claim 1 or 2, wherein the β-diketone compound to be added is dehydroacetic acid. The method for producing a vinyl chloride resin according to claim 1 (claim 4), (5) heating a β-diketone compound to a temperature higher than its melting point to form a melt, and adding the melt to a dehydrated resin cake. 5. The method for producing a vinyl chloride resin according to claim 1, 2, 3 or 4, wherein the β-diketone compounds are suspended or dissolved in water to form an aqueous mixed solution. Wherein the aqueous mixture is added to a dehydrated resin cake.
The method for producing a vinyl chloride resin described in 3, 4 or 5 (Claim 6), and (7) the β-diketone compound in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the dry resin. 7. The method for producing a vinyl chloride resin according to claim 1, wherein the compound is added in a post-treatment step after polymerization. About.

[0007]

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 having two ketone groups in a molecule such as stearoylbenzoylmethane and generally called a β-diketone compound can be used, and a compound having three or more ketone groups in a molecule, for example, a compound such as dehydroacetic acid Can also be used.

The β-diketone compounds are added in a post-treatment stage after the polymerization. The addition amount can be in the range of 0.001 to 0.5 parts by weight per 100 parts by weight of the dry vinyl chloride resin. If the number of added parts is less than 0.001 part by weight, the effect of suppressing coloration becomes insufficient, while if it exceeds 0.5 part by weight, no improvement effect commensurate with the number of added parts is obtained, which is uneconomical. Even within the above addition range, particularly 0.005 to 0.1
The addition in the range of parts by weight is particularly preferable because the balance between the number of added parts and the effect of suppressing coloring is excellent.

The method of adding the β-diketone compounds is a post-treatment step after polymerization, that is, (1) a resin slurry step after polymerization,
Alternatively, it can be added at each step of (2) a dehydration resin step after slurry dehydration, or a step of turning the dehydration resin into a dry resin powder in a dryer. The addition to the resin slurry is simple and has the merit of uniform dispersion, but some of the β-diketone compounds migrate into water, making it difficult to selectively adsorb to the vinyl chloride resin, resulting in poor addition efficiency. There is a side.

Further, the addition to the resin powder in the dryer is closer to the addition at the time of blending, but there is an advantage that it can be easily dispersed in the raw material resin.

The most preferable addition method is addition to a cake-like dewatered resin obtained by dewatering a slurry. According to this method, the β-diketone compounds can be completely adsorbed and absorbed by the vinyl chloride resin, and the above-mentioned problems can be completely solved. That is, if the β-diketone compounds are liquid at room temperature or easily melted with a low melting point, the method of adding the β-diketone compound as a liquid to the dehydrated resin is preferable. There is also a method of adding it by dissolving it. However, a method of suspending or dissolving it in water and adding it to a dehydrated resin as an aqueous mixed solution is preferable due to problems in recovery of the organic solvent and the like. These methods can be appropriately selected depending on the properties of the β-diketone compounds.

[0012] The dehydrated resin referred to herein means a resin slurry obtained by dehydrating a resin slurry obtained by polymerization with a dehydrator.
A resin containing about 20% by weight of water.

A method of uniformly dispersing in the dehydrated resin,
There is no particular limitation on the device, for example, as a method of adding,
A method of showering a β-diketone compound melt or solution to a dehydrated resin, a method of jet-mixing from a nozzle, and the like are exemplified.

Examples of the vinyl chloride resin in the present invention include a vinyl chloride homopolymer resin and a vinyl chloride copolymer resin. As a monomer copolymerizable with a vinyl chloride monomer for producing a vinyl chloride copolymer resin,
For example, alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether,
Α-olefins such as ethylene and propylene; alkyl (meth) acrylates such as methyl acrylate and methyl methacrylate; and vinylidene compounds such as vinylidene chloride.

Further, according to the present invention, the vinyl chloride resin to which β-diketone compounds can be added can be obtained by a known suspension polymerization method, and is not limited by the suspension polymerization method.

[0016]

EXAMPLES Specific examples of the present invention will be described below in detail, but the present invention is not limited to the following examples unless it exceeds the gist. (Example 1) A 3% aqueous solution of partially saponified polyvinyl acetate having an average degree of polymerization of 2000 and a saponification degree of 80 mol% was used as a dispersion stabilizer in a stainless steel polymerization machine equipped with a stirrer and a jacket having an internal volume of 1500 liters. 0.06 parts by weight (based on 100 parts by weight of vinyl chloride monomer) in terms of polyvinyl acetate, and 0.015 parts by weight of tert-butyl peroxyneodecanoate as an oil-soluble initiator. ) And 3,5,5-trimethylhexanoyl peroxide (0.02 parts by weight) were charged, and the pressure was reduced by a vacuum pump to remove oxygen. Then, vinyl chloride monomer was added to 50
0 kg was further charged, and 120 parts (same) of deionized water heated to 60 ° C. was further degassed and 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 reached 75%, the unreacted vinyl chloride monomer was recovered out of the system to terminate the reaction. Polymerization temperature (6
4 ° C.) The time from arrival to recovery was defined as the polymerization time. Table 2 shows the results. After removing the vinyl chloride monomer in the polymerization machine to the atmospheric pressure, the vinyl chloride resin slurry in the polymerization machine is discharged to a mixing tank, and sequentially dehydrated by a dehydrator using centrifugation to obtain a dehydrated resin having a water content of 15%. Was. 70 to this dehydrated resin
0.0085 parts by weight of the stearoylbenzoylmethane melt melted by heating to 100 ° C. with respect to 100 parts by weight of the dehydrated resin (0.01 parts by weight in terms of dry resin in terms of dry resin because the water content of the dehydrated resin is 15%) by a nozzle. Then, a nozzle was sprayed onto the dehydrated cake and uniformly mixed into the cake. The mixture was dried in a fluidized drier to obtain a vinyl chloride resin.
The obtained resin was blended according to the formulation shown in Table 1, and kneaded for 3 minutes using a roll having a temperature of 170 ° C. and a rotation speed of 20 rpm to prepare a roll sheet having a thickness of 0.7 mm. Using this roll sheet, a temperature of 170 ° C. and a pressure of 3
Press for 15 minutes under the condition of 0 kg / cm ² , thickness 5m
A press plate of m was prepared, 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.). The results are shown in the table. Moreover, what was blended and mixed by the composition of Table 1 was used.
40mm single screw extruder with pipe dies, cylinder temperature 160 ° C, die temperature 165 ° C, 35rpm
Extrusion was performed under the conditions described above, and air was blown into the parison discharged from the die while it was hot, to obtain a Fusen-like molded product which swelled thinly. 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. The results are shown in Table 2. 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.

[0017]

[Table 1] (Example 2) The amount of stearoyl benzoyl methane melt sprayed onto the dehydrated resin was set at 0.1 with respect to 100 parts by weight of the dehydrated resin.
The same procedure as in Example 1 was performed except that the amount was changed to 0425 parts by weight (0.05 parts by weight in terms of dry resin because the water content of the dehydrated resin is 15%). Table 2 shows the results.

Example 3 Instead of spraying a stearoylbenzoylmethane melt onto the dehydrated resin, a 10% by weight aqueous suspension of dehydroacetic acid was added to the dehydrated resin by weight of dehydroacetic acid.
The same procedure as in Example 1 was performed except that 0.0085 parts by weight (0.01 parts by weight in terms of dry resin) was added to 00 parts by weight. Table 2 shows the results.

Example 4 Instead of spraying a stearoylbenzoylmethane melt on a dehydrated resin, a stearoylbenzoylmethane melt was added to the slurry in an amount of 0.0045 parts by weight per 100 parts by weight of the slurry (water content of the slurry was 55%).
%, And 0.01 parts by weight in terms of dry resin). Table 2 shows the results.

(Example 5) Instead of spraying stearoylbenzoylmethane melt onto the dehydrated resin, when the dehydrated resin is charged into the dryer, the stearoylbenzoylmethane powder is added in an amount of 0.1 to 100 parts by weight of the dehydrated resin. The same procedure as in Example 1 was performed except that 0085 parts by weight (0.01 parts by weight in terms of dry resin) of the dehydrated resin were added and dried at the same time. Table 2 shows the results.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, and stearoylbenzoylmethane was not sprayed on the dehydrated resin. The subsequent treatment and evaluation were carried out in the same manner as in Example 1.
Table 2 shows the results.

Comparative Example 2 In the polymerization of Example 1, stearoylbenzoylmethane was added in an amount of 0.0075 parts by weight per 100 parts by weight of the vinyl chloride monomer. ) Before vacuum degassing, polymerization was performed by charging the inside of the polymerization machine, and stearoylbenzoylmethane was not sprayed on the dehydrated resin. The subsequent treatment and evaluation were performed in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 3 Comparative Example 2 was repeated except that the amount of stearoylbenzoylmethane charged to the polymerization machine was changed to 0.0375 parts (0.05 parts in terms of dry resin) based on 100 parts by weight of the vinyl chloride monomer. Was performed in the same manner as in Comparative Example 2. Table 2 shows the results.

Comparative Example 4 Comparative Example 1 was repeated except that stearoylbenzoylmethane was added in an amount of 0.01 part by weight based on 100 parts by weight of the dry resin during blending, and roll evaluation and extrusion evaluation were performed. The same was done. Table 2 shows the results.

Comparative Example 5 The procedure of Comparative Example 4 was repeated except that the amount of 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.

[0026]

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

(1) Examples 1 to 5 in which β-diketone compounds were added in the post-polymerization treatment stage, Comparative Examples 2 and 3 in which β-diketone compounds were added before polymerization, and Comparative Examples 4 and 5 in which they were added during blending In both cases, the b value indicating the degree of yellowing of the press plate was lower than that in Comparative Example 1 in which no β-diketone compound was added, indicating that the β-diketone compound has an effect of suppressing coloration. Further, the coloring suppression effect in the same addition method is correlated with the number of added parts of β-diketone compounds.

(2) Comparative Examples 2 and 3 in which the β-diketone compound was added before the polymerization were compared with Examples 1 to 5 in which the β-diketone compound was not added during the polymerization. It can be seen that the scale adhered more and the amount of fish eyes was larger in Comparative Examples 2 and 3 than in Examples 1 to 3 in proportion to the scale adhesion.

(3) Comparative Examples 4 and 5 in which the β-diketone compound was added at the time of blending were compared with those of Examples 1 to 5 in which the β-diketone compound was not added at the time of blending. It can be seen that the plate-out to the surface or screw appears remarkably.

(4) In Examples 1 to 5 in which the β-diketone compound was added to the resin in the post-polymerization treatment step, Comparative Example 1 in which the β-diketone compound was not added and Comparative Example 2 in which the β-diketone compound was added during the polymerization And Comparative Example 3, Comparative Example 4 added during blending
It can be seen that a resin having less plate-out at the time of molding, suppressing yellowish coloring, and having less fish eyes can be obtained as compared with Comparative Examples 5 and 5.

[0031]

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.

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Claims (7)

[Claims] When a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium to produce a vinyl chloride resin, A method for producing a vinyl chloride resin, comprising adding a β-diketone compound in a post-treatment step after polymerization. 2. The β-diketone compound to be added is β-diketone compound.
2. The method for producing a vinyl chloride resin according to claim 1, wherein the method is a diketone compound. 3. The method for producing a vinyl chloride resin according to claim 1, wherein the β-diketone compound to be added is stearoylbenzoylmethane. 4. The process for producing a vinyl chloride resin according to claim 1, wherein the β-diketone compound to be added is dehydroacetic acid. 5. The β-diketone compound is heated to a temperature higher than its melting point to form a melt, and the melt is added to a dehydrated resin cake. A method for producing a vinyl chloride resin. 6. The method of claim 1, wherein the β-diketone compounds are suspended or dissolved in water to form an aqueous mixture, and the aqueous mixture is added to a dehydrated resin cake.
6. The method for producing a vinyl chloride resin according to 4 or 5. 7. A dry resin 10
7. The vinyl chloride system according to claim 1, 2, 3, 4, 5, or 6, which is added in a post-treatment step after polymerization so as to be 0.001 to 0.5 parts by weight per 0 parts by weight. Method of manufacturing resin.