JPS6358854B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a vinyl chloride resin paste sol (hereinafter referred to as salt pisol) by mixing an aqueous dispersion of vinyl chloride resin for paste processing with a plasticizer and separating and removing water. . As a method for producing salt pisol, an aqueous dispersion of vinyl chloride resin for paste processing obtained by polymerization is heated and dried using, for example, a spray dryer, and if necessary, the fine powder resin obtained by further pulverization is plasticized. A common method is to mechanically disperse the compound in the agent. However, in this method, not only the thermal stability of the resin is impaired due to the thermal history received in the heat drying process, but also there is a risk of undesirable coalescence of resin particles due to heat. Most of the raw materials remain on the surface of the resin powder, which impairs the thermal stability, weather resistance, transparency, etc. of the final product. Furthermore, since the resin is handled in a fine powder state, it is difficult to avoid the disadvantage that the working environment is deteriorated due to scattering and adhesion of the fine powder during transportation, transportation, and processing. Therefore, an object of the present invention is to produce a salt pisol that has improved workability and provides a final paste processed product with excellent properties without going through the heat drying process of vinyl chloride resin after polymerization. There is a particular thing. This object of the present invention is a vinyl chloride resin for paste processing (hereinafter sometimes referred to as vinyl chloride resin) obtained by polymerizing a vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride in an aqueous medium. 25
An aqueous dispersion containing ~80% by weight, a plasticizer, and an organic solvent that does not substantially dissolve the vinyl chloride resin and is compatible with the plasticizer, in an amount of 20~80% by weight of the plasticizer per 100 parts by weight of the vinyl chloride resin. 1500 parts by weight and 0 organic solvents
After the vinyl chloride resin is transferred to a plasticizer layer or a mixed layer of a plasticizer and an organic solvent by mixing in a proportion of ~40 parts by weight, this layer is separated from an aqueous layer, and then dehydrated. This is accomplished by recovering the plasticizer as a salt pizol, and performing all of these operations under conditions in which the vinyl chloride resin does not substantially absorb the plasticizer. That is, the present invention basically consists of the following three steps. 1 An aqueous dispersion of vinyl chloride resin and a plasticizer or a plasticizer and an organic solvent (hereinafter, when both are collectively referred to as
A process in which the vinyl chloride resin is mixed with a plasticizer, etc.) and transferred to the plasticizer layer. 2. A step of separating a plasticizer layer containing vinyl chloride resin (salt pisol layer) from the aqueous layer. 3. A step of removing the water remaining in the salt pizol layer (and the organic solvent if unnecessary as a salt pizol component) and recovering the salt pizol. The aqueous dispersion of vinyl chloride resin for paste processing used in the present invention is a homopolymer of vinyl chloride or mainly composed of vinyl chloride (usually 70% by weight or more), along with vinyl acetate, vinylidene chloride, ethylene, acrylonitrile, It refers to an aqueous dispersion of a copolymer with an olefinic monomer such as acrylic acid ester or maleic acid, and is not particularly limited as long as it can be subjected to normal paste processing.
If necessary, a vinyl chloride resin for weight expansion can also be included. The content of vinyl chloride resin in the aqueous dispersion is 25
~80% by weight. That is, it is convenient to use an aqueous dispersion of vinyl chloride resin after polymerization, but it is also possible to partially dehydrate it or add water if necessary. However, if it is less than 25% by weight, it is unsuitable because the production efficiency will drop significantly, and if it exceeds 80% by weight, it cannot exist as a fluid aqueous dispersion, so it cannot be mixed with plasticizers etc. Difficult to mix. The plasticizer to be mixed with the aqueous dispersion of vinyl chloride resin is particularly limited as long as it is used in paste processing, such as dioctyl phthalate, diisodecyl phthalate, diheptyl phthalate, dibutyl phthalate, butylbenzyl phthalate, dioctyl adipate, etc. Not done. The amount used is not particularly limited and is in the range of 20 to 1,500 parts by weight per 100 parts by weight of the vinyl chloride resin. In applications where a large amount of plasticizer is used, a great deal of labor is generally required to mix the plasticizer, but according to the present invention, production efficiency can be greatly improved. If it is less than 20 parts by weight, shaping during heating and melting becomes difficult;
If it exceeds 1500 parts by weight, practical strength as a paste processed product cannot be obtained. In the present invention, the vinyl chloride resin is not substantially dissolved (it may be slightly swollen),
In addition, by using an organic solvent that is compatible with the plasticizer in combination with the plasticizer, it may be possible to efficiently transfer the vinyl chloride resin to the same layer as the plasticizer. Specific examples of the organic solvent include aliphatic or aromatic hydrocarbons, ketones, esters, and ethers. The amount used is 0 to 40 parts by weight per 100 parts by weight of vinyl chloride resin. If this organic solvent remains in the salt pisol, it has the effect of lowering the viscosity of the system, so it may be suitable to use it in combination when the amount of plasticizer used is 100 parts by weight or less. However, since there is a risk of environmental pollution due to volatilization during paste processing, the amount used should not exceed 40 parts by weight. In the first step of the present invention, the vinyl chloride resin in the aqueous dispersion transfers to the plasticizer layer by contact with the plasticizer, etc., but in order for this transfer to occur efficiently, the aqueous dispersion and the plasticizer etc. It is necessary that these are sufficiently mixed. As the mixer, a stirring tank mixer, a non-stirring shaking mixer, a non-stirring tower mixer, a pipe mixer, etc. are used. Next, the salt pisol layer obtained by transferring the vinyl chloride resin to the plasticizer layer is separated from the aqueous layer. If the two layers can be easily separated by standing still, a normal sedimentation separator may be used;
When separation by standing still is difficult or requires a long time, a centrifugal sedimentation type separator is generally used. Furthermore, if the salt pizol layer has a high vinyl chloride resin content and the resin is granular, it is also possible to separate the aqueous layer using a screen or the like. Since the salt pisol thus obtained still contains a considerable amount of water, it is difficult to use it as is for paste processing. Further, when an organic solvent is used in combination, if it is unnecessary or becomes a nuisance as a salt pisol component, it is necessary to remove the organic solvent. Therefore, as a third step prior to recovery, residual moisture and organic solvent are usually removed by vacuum evaporation at around room temperature. For this purpose, for example, a falling film evaporator, a stirring liquid film evaporator, or the like can be used in combination with an oil rotary pump, a steam ejector, or the like. On the other hand, vinyl chloride resin may remain in the water layer separated from the salt pizol layer, so in this case, the vinyl chloride resin can be removed by recycling the water layer to the first or second step. It is desirable to increase the recovery rate. The salt pisol obtained by the present invention must be a dispersion of vinyl chloride resin in a plasticizer, etc., and the vinyl chloride resin must not substantially absorb the plasticizer, etc. If plasticizers and the like are absorbed into the vinyl chloride resin, the viscosity of the resulting salt pisol will increase, making it impossible to use it for paste processing. Therefore, in the present invention, it is necessary to select conditions such that the vinyl chloride resin does not absorb the plasticizer throughout the entire process. The main condition is temperature, which must be maintained at 0-70°C, preferably 20-50°C throughout the entire process. The thus obtained salt pisol of the present invention is appropriately mixed with compounding agents used in conventional paste processing of vinyl chloride resin, such as heat stabilizers, fillers, pigments, viscosity reducers, and plasticizers as additional components. However, in some cases, these compounding agents can be added to the salt pisol after separation of the aqueous layer in the present invention but before removal of residual water. The effects of the present invention are as follows. (1) The salt pisol of the present invention can be subjected to paste processing in the same manner as conventional salt pisol. (2) Since there is no heat drying process, the vinyl chloride resin particles do not coalesce and are extremely finely dispersed in the plasticizer, etc., and therefore have good processability. For example, it is possible to prevent the streaking phenomenon that is often a problem in thin film coating processing. (3) Since auxiliary raw materials such as emulsifiers used during polymerization are also distributed to the aqueous layer side during the separation and removal process of the aqueous layer, the salt pisol of the present invention has a lower content of auxiliary raw materials than conventional salt pisol, Therefore, the thermal stability during molding, the transparency and weather resistance of the molded product are improved. (4) Since vinyl chloride resin is not taken out as a dry powder, it is possible to prevent the working environment and working efficiency from deteriorating due to powder handling during transportation, processing, etc. At first glance, the present invention may be confused with the method disclosed in Japanese Patent Publication No. 26-669, in which an aqueous dispersion of vinyl chloride resin and a plasticizer are mixed and then water is removed. However, this method attempts to prepare a fluid plasticized powder in which a plasticizer is sufficiently absorbed into a vinyl chloride resin for the purpose of shortening the plasticization time during processing. Therefore, the temperature during the plasticization treatment must be such that the vinyl chloride resin can absorb as much plasticizer as possible and still be able to obtain it in powder form, that is, at a temperature close to 100°C. 6 for polymers to achieve
It is required to use ~15 times the volume of water;
Furthermore, in order to obtain the plasticized product in powder form, a drying process must be performed. Moreover, the thermal history due to plasticization and drying of the vinyl chloride resin is incomparably more severe than that in the present invention. Furthermore, the invention of U.S. Patent No. 3,067,162 lowers the plasticizing temperature to 40 to 60°C in the invention of Japanese Patent Publication No. 26-669, but instead adds a plasticizer as an emulsion. It is understood that this invention improves the absorption of plasticizer into resin particles, so this invention is also basically based on the
- It is based on the same technical idea as the invention of No. 669. Moreover, in this US patent, the plasticizer is emulsionized as described above, so one must be prepared for the adverse effects of the emulsifier used thereon on product quality. As described above, these known methods are completely different from the method of the present invention in terms of technical idea, purpose, and structure. Next, the present invention will be explained by examples. Note that the number of parts of the compounding agent is the number of parts by weight per 100 parts by weight of the vinyl chloride resin. Example 1 250 g of vinyl chloride resin latex for paste processing (resin content 47% by weight) and 50 g of dioctyl phthalate were shaken at room temperature for 30 minutes in a separatory funnel, and then left to stand for 2 hours. layer) and an aqueous layer. The plasticizer layer was collected and vacuum dehydrated using a rotary evaporator and an oil rotary vacuum pump to obtain salt Pisol A containing 60 parts of dioctyl phthalate. A mixture of 2 parts by weight of a Ca/Zn-based liquid heat stabilizer per 100 parts by weight of vinyl chloride resin was added to this salt pizol and applied onto a glass plate to a thickness of 0.4 mm, and heated in a hot air oven at 190°C for 10 minutes. As a result, a transparent soft sheet was obtained. Example 2 250 g of vinyl chloride resin latex for paste processing (resin content 19% by weight) and 50 g of dioctyl phthalate were placed in a beaker, stirred with a propeller stirrer for 30 minutes at room temperature, and then left to stand for 2 hours, resulting in a plasticizer layer. and an aqueous layer. After removing the aqueous layer, the plasticizer layer was dehydrated in the same manner as in Example 1.
A salt pisol B was obtained containing 50%. After adding 1 part of Ca/Zn-based liquid heat stabilizer and 120 parts of calcium carbonate to this salt pisol and kneading and dispersing it, the mixture was poured into a suitable mold and heated at 110°C for 30 minutes in a hot air oven. , an opaque eraser was obtained. Example 3 200 g of vinyl chloride resin latex for paste processing (resin content 47% by weight), 50 g of vinyl chloride resin slurry for bulking (resin content 30% by weight), and 50 g of dioctyl phthalate were placed in a wide-mouthed polyethylene bottle and shaken at room temperature for 30 minutes. After shaking with a shaker, the mixture was allowed to stand for 2 hours, and was separated into a plasticizer layer and an aqueous layer. After removing the aqueous layer, the plasticizer layer was subjected to the same dehydration operation as in Example 1 to obtain salt Pisol C containing 70 parts of dioctyl phthalate. Add 3 parts of Ca/Zn liquid thermal stabilizer to this salt pizole.
After partial kneading and dispersion, rotational molding was performed at 230°C for 5 minutes to obtain a translucent hollow molded product. Example 4 250 g of vinyl chloride resin latex for paste processing (resin content 47% by weight), dioctyl phthalate
Put 25g and 25g of butylbenzyl phthalate into a beaker and stir with a propeller stirrer for 30 minutes at room temperature, then introduce the mixture into a centrifuge and stir at 7000rpm.
When the separation operation was performed for 20 minutes, a resin precipitate layer,
It was separated into a plasticizer layer and an aqueous layer. After removing the aqueous layer, the precipitate layer and the plasticizer layer were stirred for 10 minutes using a propeller stirrer to make both layers homogeneous, and dehydration was performed in the same manner as in Example 1. The total amount of plasticizer was 44. A salt Pisol D was obtained containing 50%. After kneading and dispersing 10 parts of Mineral Spirit A (manufactured by Nippon Petrochemical Co., Ltd.) and 3 parts of an organic tin-based heat stabilizer in this salt pizol, it was applied to a thickness of 0.2 mm on a steel plate whose surface had been treated with an adhesive. When heated at 210°C for 2 minutes in a far-infrared heating conveyor oven, a film that adhered well to the steel plate was obtained. Example 5 An experiment similar to Example 1 was conducted except that 40 g of dioctyl phthalate and 10 g of mineral spirits were used instead of the 50 g of dioctyl phthalate used in Example 1, and a salt pisol containing a total of 55 parts of both was obtained. E was obtained. After kneading and dispersing 20 parts of dibutyl phthalate, 2 parts of an organic tin-based heat stabilizer, and 2 parts of a gelling agent in this salt pisol, it was applied by dip coating onto the surface of a glass bottle, and heated in a hot air oven at 190°C for 15 minutes. However, a transparent protective film was formed on the surface of the glass bottle. Example 6 A similar experiment was conducted using the same amount of diisodecyl phthalate in place of the dioctyl phthalate used in Example 1, and a salt Pisol F containing 55 parts by weight of diisodecyl phthalate was obtained. Reference Example The characteristics of the salt pisols A to F obtained in Examples 1 to 6 were evaluated. Display the results. In addition, ordinary salt pisol prepared by adding plasticizer etc. to the vinyl chloride resin powder for paste processing in the same parts as in each example (corresponding to the order of examples, a, b,
c, d, e, f) are also listed.

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Claims (1)

[Claims] 1 An aqueous dispersion containing 25 to 80% by weight of a vinyl chloride resin for paste processing obtained by polymerizing a vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride in an aqueous medium, a plasticizer, and vinyl chloride. An organic solvent that does not substantially dissolve the resin and is compatible with the plasticizer in a ratio of 20 to 1,500 parts by weight of the plasticizer and 0 to 40 parts by weight of the organic solvent per 100 parts by weight of the vinyl chloride resin. After the vinyl chloride resin is transferred to a plasticizer layer or a mixed layer of plasticizer and organic solvent by mixing, this layer is separated from the water layer and then dehydrated, and then recovered as a vinyl chloride resin paste sol. A method for producing a vinyl chloride resin paste sol, characterized in that all of these operations are carried out under conditions in which the vinyl chloride resin does not substantially absorb a plasticizer.