JPH02134215A - Manufacture of vinyl chloride resin for use in processing of granular paste - Google Patents

Abstract

PURPOSE:To reduce the generation of dusts when a vinyl chloride resin is mixed with a plasticizer or it is turned into sol by using an apparatus which has a specific surface smoothness at least at a conical part among the inner walls thereof to be in contact with granular bodies. CONSTITUTION:A water disperse liquid of a vinyl chloride resin for processing paste is dried and granulated by a spray dryer. The spray dryer for drying and granulating the water disperse liquid is such that has a smoothness not smaller than #100 by buffing at least at the surface of a conical part thereof among the inner walls to be in contact with granulated bodies. At this time, the water disperse liquid is first atomized by atomizer in the spray dryer, and then dried, whereby granulated bodies are produced. The granulated bodies are taken outside the system. The granulated bodies obtained in this method are apt to decrease its readiness to be turned into sol if exposed to a high temperature for a long time. Therefore, if the granulated bodies are arranged not to remain in the spray dryer for a long time, e.g., about four hours or longer at 50 deg.C, the granulated bodies can be vinyl chloride resin for processing granular paste, having a good property to be turned into sol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a vinyl chloride resin for processing particulate pastes. More specifically, the present invention relates to a method for producing particulate vinyl chloride resin for paste processing which has excellent solubility from an aqueous dispersion of vinyl chloride resin for paste processing obtained by suspension polymerization or emulsion polymerization.

[Prior art/problems to be solved by the invention] Conventional vinyl chloride resins for paste processing are produced by suspension polymerization or emulsion polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in the presence of a surfactant. An aqueous dispersion of vinyl chloride resin is obtained, which is spray-dried and then usually pulverized and supplied as a product.

PVC resin for paste processing is supplied in finely ground form, which is mixed with a plasticizer and made into a sol (this is called sol formation), then molded and processed through a hardening process called gelation (heating process). ), but if vinyl chloride resin is difficult to convert into a sol, or if there are unsolvable substances in the sol, problems may occur during the molding process, and the quality of the final product may be affected. This is because the problem of dropping the item may occur.

However, since the vinyl chloride resin for paste processing is in the form of finely ground powder, the work environment may deteriorate due to the generation of dust during the solization process during processing, such as the generation of dust when opening the bag.
Problems arise, such as the inability to automatically measure and supply powder.

In order to solve the above problem, attempts have been made to granulate vinyl chloride resin for paste processing.

For example, a method has been proposed for spray drying an aqueous dispersion of vinyl chloride resin by lowering the temperature of the drying air to produce granules with excellent powder characteristics and good solability ( (See Japanese Patent Publication No. 57-5815 and Japanese Patent Application Laid-Open No. 80-120728).

However, even when granulated by these methods, there is a problem that a large number of undispersed granules that have not been completely sol-formed remain in the sol obtained by sol-forming.

[Means for Solving the Problems] As a result of intensive research to solve the above-mentioned problems with conventional vinyl chloride resin for paste processing, the present inventors have developed an aqueous dispersion of vinyl chloride resin for paste processing. We discovered that when drying and granulating in a spray dryer, if the granules adhering to the inside of the dryer are exposed to heat for a long time, the amount of undispersed granules increases in the sol, and we are working to reduce this adhesion. As a result, it was discovered that the amount of undispersed granules in the sol was reduced, and the granules of vinyl chloride resin for paste processing, which had excellent sol-forming properties, could be replaced, and the present invention was completed.

That is, in the present invention, when drying and granulating an aqueous dispersion of vinyl chloride resin for paste processing with a spray dryer,
The present invention relates to a method for producing a vinyl chloride resin for particulate paste processing, which uses an apparatus in which at least the surface of the conical part of the inner wall surface of the apparatus with which the granules come into contact has a smoothness of buff finish #100 or higher.

[Example] In the present invention, an aqueous dispersion of a vinyl chloride resin for paste processing is dried and granulated using a spray dryer.

The aqueous dispersion of vinyl chloride resin for paste processing is obtained by suspension polymerization or emulsion polymerization of vinyl chloride or a heptamer mixture mainly composed of vinyl chloride in the presence of a surfactant. The dispersion is similar to the aqueous dispersion that is produced for producing vinyl chloride resin for paste processing, and there is no particular limitation as long as it is such a dispersion.

The spray dryer used for drying and granulating the aqueous dispersion prepared in this manner must have at least a cone surface with a smoothness of buff finish #100 or higher among the inner wall surfaces of the device that come into contact with the granules. There is no particular limitation as long as the device has this, and any commonly used device may be used. As a specific example of such a spray dryer, for example, "Spray Drying Handbook (SP
RAY DRY INCII AND BOOK) J (K, Masters), 3rd edition, 1
In 979, George O. Gottwin & Co.
Various spray dryers such as those shown in Figure 4.10 on page 121 can be mentioned.

When granulating an aqueous dispersion of vinyl chloride resin for paste processing using a spray dryer, the aqueous dispersion is first atomized by an atomizer inside the spray dryer, then dried to produce granules, which are then released from the system. taken out.

The granules obtained in this way are sensitive to heat and tend to deteriorate in solubility when exposed to a high-volume environment for a long time. By preventing the residence time for more than a certain period of time, a vinyl chloride resin for particulate paste processing with good solubility can be obtained.

Typical examples of the parts that the granules come into contact with include the surface of the conical part at the bottom of the dryer, the top wall of the dryer, and the side walls of the dryer. In the present invention, it is necessary that at least the surface roughness of the conical portion be buffed to #100 or higher.

The conical part serves to guide the granules, which have been granulated and dried in the dryer interior space, to the lower part of the conical part and encourage them to be discharged outside the dryer. The adhesion of granules is reduced, the granules exposed to heat for a long time are reduced, and as a result, the solubility of the granules is improved.

While the spray dryer is operating, the granules attached to the inner wall of the spray dryer are removed by vibrating the main body of the spray dryer or by applying air flow to the inner wall of the spray dryer. Adhesion to the inner wall of the body is further reduced, and as a result, the solubility of the granules is further improved.

The size of the particles granulated from the aqueous dispersion is preferably such that the average particle size is about 30 to 100 μm, which is a size that does not cause problems when finely pulverized and is easy to form into a sol, and is preferably 40 to 60 μm. It is more preferable that it be about the same level.

The conditions for granulation include, for example, the temperature of the air used for drying is 150°C or lower, preferably 100°C or lower, and the temperature of the exhaust air exiting the dryer is 60°C or lower, preferably 50°C or lower. As such, conditions that have been generally adopted may be used.

In this way, it has a sol-forming property comparable to that of the conventionally used finely pulverized vinyl chloride resin for paste processing, and it is possible to avoid deterioration of the working environment due to the generation of dust when opening bags, etc. Problems such as the inability to carry out automatic metering and feeding of particles have been solved.The average particle size is 30 to 100 degrees, and the angle of repose, which is one of the indicators of powder properties, is 30 to 40 degrees.
When evaluated using the method for measuring the size of undispersed matter in the sol described later, the size of undispersed matter was 50. A particulate vinyl chloride resin for paste processing as shown below is produced.

Next, the method of the present invention will be explained based on examples.

In addition, the sol properties and the average particle diameter of the granules were evaluated by the following method.

(Size of undispersed matter in the sol) 500 g of granules and 325 g of dioctyl phthalate were placed in a 5 g Hobart mixer (manufactured by Hinayo Kogyo, SDMV type), and rotated at 141 rpm with a hook propeller at 25°C.
Mix and stir for 10 minutes at a revolution speed of 67 rpm to produce a sol. The size of undispersed matter in the sol is determined by JIS K.
Measured according to the test method in 4.4 of ``5400r Paint General Test Methods'' and judged using Method A. In other words, pour the sol into the groove of the grain gauge, squeeze it with a scraper, and create a layer of sol in the groove so that the thickness changes continuously from 100 to 0. By reading the thickness of the layer, estimate the diameter of the agglomerates present in the sol.

(Number of undispersed substances in the film) Using a film applicator with a clearance of 152 mm, the sol used for measuring the "size of undispersed substances in the sol" was spread on a glass plate, and the sol was heated at 200°C. 4 in the oven
A film is prepared by gelling for a few minutes. Cut out a sample measuring 3 cm x 3 cm from this film.
Count the fish eyes in the sample with the naked eye.

(Average particle size of granules) If the particle size is 100 or more, it is classified using a sieve, and if it is smaller than that, the particle size distribution is measured using a Coulter counter to determine the average particle size.

Comparative Example 1 A spray dryer with an Nα2B surface finish in accordance with JIS G 4305 (column diameter: 2.75 m, tower length: 3 m for the straight body part, 2.2 m for the conical part, and 2.2 m for the conical part angle). An aqueous dispersion of vinyl chloride resin for paste processing with a solid content concentration of 47% was sprayed using a rotating disk type atomizer, and the drying air inlet temperature was 80°C and the exhaust air temperature was 45°C.
It was dried under conditions of ℃ to obtain granules for evaluation. During drying, an air hammer attached to the main body of the spray dryer was activated once every 20 seconds.

When the inside of the dryer was observed after the drying was completed, a large amount of granules were found to have adhered to the surface of the conical part. When some of them were collected and observed under a microscope, agglomerates consisting of several granules were found here and there. Such lumps were present in the recovered granules in an amount of 2% by weight or more. Table 1 summarizes the drying conditions and powder characteristics of the granules, the size of undispersed particles in the sol produced from the granules, and the evaluation results of the number of undispersed particles in the film. .

Example 1 A granule was obtained under the same conditions as in Comparative Example 1, except that the surface of the conical part of the dryer was buffed to #240i.

When the inside of the dryer was observed after the drying was completed, almost no granules were observed on the surface of the conical part.

Table 1 shows the results of the same evaluation as in Comparative Example 1.

[Margins below] Table 1 From the results in Table 1, it can be seen that the size of undispersed matter in the sol is considerably smaller in Example 1 than in Comparative Example 1, and the number of undispersed matter in the film is also smaller. I understand.

Examples 2 to 4 and Comparative Examples 2 to 3 Ni 2 according to JIS G 4305 was attached to the conical part inside the dryer.
D (no polishing), Na2B (no polishing), buff #1
00° Buff # 150. A test piece with a surface finish of #240 was attached and a drying experiment was conducted under the same conditions as in Example 1. After the experiment was completed, the test pieces were taken out and observed, and found that a large amount of granules were attached to the k2DSk2B test piece, but Buff #10G and Buff #15
No granule adhesion was observed on the test pieces of #0 and #240.

This shows that if the surface finish of the conical part of the spray dryer is made as smooth as buffing material 100 or higher, adhesion of granules can be prevented and the generation of undispersed matter can be reduced.

[Effects of the Invention] The granules of vinyl chloride resin for paste processing obtained by the method of the present invention have good flowability because they are granules, and have little fine powder, so they are free from dust when mixed with plasticizers and when made into sol. The problem of generation is also reduced, and the sol-forming properties are excellent.

Claims (1)

[Claims] 1. When drying and granulating an aqueous dispersion of vinyl chloride resin for paste processing in a spray dryer, at least the surface of the conical part of the inner wall surface of the device that comes into contact with the granules should have a smoothness of buff finish #100 or higher. 1. A method for producing a vinyl chloride resin for particulate paste processing, characterized by using an apparatus having the following.