JPH0124175B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a granular vinyl chloride resin composition that is subjected to paste processing. Normally, when paste processing vinyl chloride resin, the vinyl chloride resin (hereinafter referred to as resin) manufactured for paste processing is mixed with plasticizers, stabilizers, pigments, fillers, etc. as necessary. A method is adopted in which the plastisol is mixed with an agent to form a liquid plastisol and then subjected to a molding process. A molded article is then obtained by shaping the liquid plastisol by means such as casting, coating and dipping, and heating it to melt and solidify it. Therefore, the fluidity properties of plastisol are properties that have an extremely important effect on the formability of paste processing, and the reality is that great effort and ingenuity are put into the formulation, especially in the quality design of the resin. be. On the other hand, in addition to the flow characteristics of plastisol, the dispersibility of the powder compound into the liquid compound has a large influence on the properties, particularly the appearance and strength, of the molded article. If powder compounding agents, such as resins, remain in the sol as coarse aggregates, it not only affects the fluidity of the plastisol, but also causes clogging during transportation of the sol, streaking during coating processing, etc. This causes problems such as roughening of the molded product's skin, matting, and even a decrease in strength. In consideration of such problems in paste processing, the reality is that resin is usually supplied as a fine powder, such as a JIS sieve 325 mesh. As a method for producing resin for this purpose, vinyl chloride or a monomer mixture mainly composed of vinyl chloride is mixed in the presence of a radical-generating polymerization initiator and an emulsifier.
Particle size can be adjusted by emulsion polymerization or suspension polymerization.
A method has been adopted in which an aqueous dispersion of spherical resin of 0.05 to 5 μm is obtained and this aqueous dispersion is spray-dried. However, the resin obtained by this method contains all the nonvolatile components in the aqueous resin dispersion, which causes a decrease in properties such as thermal stability, water resistance, and transparency of the molded product. Furthermore, in normal spray drying, the resin particles in the sprayed aqueous dispersion are dried and captured as resin particle aggregates as the water evaporates, so a pulverization process may be required in order to ship the product. Even with these treatments, it is often not possible to achieve dispersion of aggregated particles through simple mixing during plastisol production.
Furthermore, as mentioned above, since resin is a fine powder, it causes a deterioration of the working environment, such as powder scattering when products are packed into bags, and when plastics are opened and mixed when bags are opened and mixed. In addition, poor powder fluidity makes automatic weighing and transportation difficult. As a result of studying the current problems with resins for paste processing, the present inventors have determined that (a) a plasticizer and, optionally, (b) compatibility with the plasticizer, are added to the aqueous dispersion of vinyl chloride resin for paste processing. An organic liquid that does not substantially dissolve the vinyl chloride resin and is sparingly soluble in water is used (if an organic liquid is used, the total amount including the plasticizer) in an aqueous dispersion of the vinyl chloride resin. The same volume or less as the liquid, and vinyl chloride resin
After mixing at a ratio of 15 parts by volume or more to 100 parts by volume to transfer the vinyl chloride resin to a plasticizer phase or a mixed phase of plasticizer and organic liquid, the aqueous phase is separated and removed, and then Obtaining a plasticizer-containing vinyl chloride resin granular composition by drying a phase containing a vinyl chloride resin and a plasticizer or a plasticizer and an organic liquid, and performing these operations at 70°C or lower. This makes it possible to achieve uniform dispersion with simple mixing during the production of plastisol, and also provides molded products with excellent thermal stability, water resistance, and transparency. It was confirmed that a vinyl chloride resin composition could be obtained, and the present invention was completed. The method of the present invention basically consists of the following steps. That is, (1) the first step of mixing the aqueous dispersion of the resin and the plasticizer (and organic liquid) and transferring the resin to the plasticizer (and organic liquid) phase; (2) removing the aqueous phase from the mixed liquid. (3) a third step of drying a mixture mainly consisting of a plasticizer (and organic liquid) and a resin. These steps include (4) the step of recovering the resin from the aqueous phase separated in the second step, (5) (4)
A step may be added in which the resin recovered in step 1 is dried alone or mixed with the mixture in step 3.
Furthermore, (6) incorporating a granulation step into the first to third steps is effective in achieving the effects of the present invention. The aqueous dispersion of vinyl chloride resin for paste processing used in the present invention is a vinyl chloride homopolymer produced by conventional emulsion polymerization or suspension polymerization, or mainly consists of vinyl chloride (usually 70% by weight or more). An aqueous dispersion of a copolymer of this and an olefinic monomer such as vinyl acetate, vinylidene chloride, ethylene, acrylonitrile, acrylic acid ester, or maleic acid, which can be subjected to normal paste processing. There are no particular restrictions.
If necessary, a vinyl chloride resin for weight expansion can also be included. The content of vinyl chloride resin in the aqueous dispersion is 10
~80% by weight. That is, it is convenient to use the aqueous dispersion of vinyl chloride resin after polymerization as it is, but it is also possible to partially dehydrate it or add water if necessary. However, 10
If it is less than 80% by weight, it is unsuitable because the production efficiency will drop significantly, and if it exceeds 80% by weight, the plasticizer (and organic liquid) cannot exist as a fluid aqueous dispersion. It is difficult to mix with 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. However, plasticizers with high gelling properties for resins, such as diethyl phthalate, must be used with caution in view of the storage stability of the resulting granular composition. Further, the amount used is preferably such that the mixing ratio is equal to or less than the porosity between the resins when the resin is packed in the resin. If a plasticizer with a porosity higher than the porosity is used, the granular composition may cause blocking, which may cause problems in terms of storage and distribution.
When commercially available resin particles for paste are packed close-packed, the porosity between the resins is usually about 0.3 to 0.4.
It is believed that it is possible to reduce the particle size to around 0.14 by optimizing the particle size distribution of the resin. The organic liquid used as necessary must have a boiling point or 90% evaporation temperature of -15 at normal pressure.
The material used is one that is sparingly soluble in water at temperatures between 10°C and 200°C, is compatible with plasticizers, and does not dissolve resins. Those with a boiling point or 90% evaporation temperature lower than -15°C are not economical, as they require sophisticated mixing and separation operations with aqueous dispersions, as well as organic liquid recovery operations and equipment, and are not economical. If the temperature exceeds 100%, it becomes necessary to operate at higher temperatures during the drying process of the resin composition trapped in the organic liquid phase, resulting in the plasticizer in the resin composition being dissolved and absorbed into the resin. This should be avoided since there is a risk that the composition will not become a plastisol, or even if it does become a plastisol, it will be a composition that provides an extremely high viscosity sol. Of course, even if such a high boiling point or low vapor pressure organic liquid is used, the purpose of the present invention can be achieved by drying it at low temperature for a long time under reduced pressure, but this is not an economical method. do not have. The purpose of using the organic liquid is to lower the viscosity of the plasticizer, improve the abundance ratio of the organic liquid phase containing the plasticizer to the aqueous medium, promote the transition of the resin to the plasticizer phase, and improve the efficiency of the transition. Since the purpose of the organic liquid is to improve the performance of plasticizers and resins, it is necessary that the organic liquid be chemically and physically inert to the plasticizer and resin, and it is not preferable that the organic liquid dissolves or significantly swells the resin. The organic liquid must also be compatible with the plasticizer. Furthermore, the lower the solubility of the organic liquid in water, the easier the wastewater treatment of the aqueous phase to be separated, and the less loss of the organic liquid.
Industrially preferred. In addition, if the organic liquid dissolves the resin or strongly swells, not only will it take time and equipment to recover the organic liquid, but the resin composition obtained by drying will The dispersibility during sol preparation is markedly reduced, and the plastisol obtained from this composition has a markedly unstable viscosity, making it impossible to achieve the object of the present invention. From this point of view, examples of organic liquids include paraffinic hydrocarbons such as butane, hexane, and octane; naphthenic hydrocarbons such as cyclohexane, methylcyclopentane, and tetralin; aromatic hydrocarbons such as isopropylbenzene and diethylbenzene; Examples include mineral spirits, which are mixtures of mineral spirits, petroleum solvents such as mineral turpentine, and halogenated hydrocarbons such as carbon tetrachloride, trichlene, and freon. Further, esters, ethers, alcohols, and ketones may also be used as long as they are sparingly soluble in water and do not dissolve the resin.
When used as a mixed organic liquid, one of the components may dissolve or swell the resin as a single component, but it does not matter if the mixed liquid satisfies the above conditions. The total amount of plasticizer (and organic liquid) used must be equal to or less than the volume of the aqueous resin dispersion, and at least 15 parts by volume per 100 parts by volume of the resin in the aqueous dispersion. Plasticizer (plus organic liquid)
When the amount is greater than that of the aqueous dispersion of resin and mixed with the aqueous dispersion of resin, a water-in-oil emulsion is formed, and the resin can be trapped in the plasticizer (and organic liquid) phase and separated and recovered. Not only does this create a risk of drying the composition, but it also consumes unnecessary energy and is uneconomical in the drying process of the composition. On the other hand, if the amount of plasticizer (total of organic liquid) is less than 15 parts by volume per 100 parts by volume of resin, the rate of transfer of the resin to the plasticizer phase decreases, which is disadvantageous. The total amount and respective amounts and types of plasticizer and organic liquid will depend on the desired composition of the final composition (plasticizer content) and the shape of the resin mixture entrapped in the plasticizer (and organic liquid) phase as described above. It can be selected arbitrarily within the specified range. For example, when attempting to separate and granulate a mixture of resin and plasticizer (and organic liquid) into spherical granules with considerable physical strength, The amount of plasticizer (total of organic liquid) should be adjusted so that it is at least 30% and less than 100% of the void volume between. Mixing of the plasticizer (and organic liquid) and the aqueous resin dispersion is usually carried out at a temperature of 20 to 70°C, but when using an organic liquid, equipment and operational considerations depend on its vapor pressure. Just choose the optimal point. Generally, operating at high temperatures reduces the viscosity of the plasticizer (and its mixture with organic liquid) and reduces the interfacial tension between it and water and resin, thus promoting the transition of the resin into the plasticizer phase. The temperature is preferably 50℃ because the higher the temperature, the faster the resin will swell due to the plasticizer and organic liquid.
It should be: Above 70°C, there is a risk that not only will the plasticizer be absorbed into the resin faster, but the resin will soften and coalesce, making the final composition no longer suitable for pasting. Next, to separate the aqueous phase from the resin mixture trapped in the plasticizer (and organic liquid) phase, a known method may be used depending on the shape of the trapped resin mixture. For example, if the amount of plasticizer (and organic liquid) used is reduced to achieve liquid granulation, the aqueous phase can be separated by means such as a screen. The mixture of resin particles and plasticizer (and organic liquid) separated in the separation process is then sent to a drying process to remove the organic liquid and attached moisture. In this drying process, it is necessary to set conditions such that the strength of resin aggregation and coalescence does not impair the dispersibility of the product composition during paste processing. That is, during the drying process, the temperature of the resin composition to be dried is 70°C or less,
Preferably, the temperature is 50°C or lower. As the drying device, from the viewpoint of maintaining the temperature of the material to be dried low and recovering the organic liquid, it is preferable to use a reduced pressure stirring dryer, band dryer, or rotary dryer, but widely known drying devices can be used. It is possible. In the drying process, it is possible to obtain a resin composition with an amorphous shape or a wide particle size distribution as a product by appropriately selecting the equipment, but it is possible to use a pellet forming machine such as an extrusion type granulator during the process. It is also possible to homogenize the particle shape by incorporating. In this case too,
During granulation, the resin composition must not melt due to heat or pressure or absorb plasticizer, which may impair dispersibility during paste processing. Through such a drying process, a granular resin composition is obtained. Note that the plasticizer appears to be present between the resin particles and to function as a binder between the particles. When carrying out the method of the present invention industrially, it is necessary to increase the transfer rate of the resin to the plasticizer (and organic liquid) layer in the first step, and to increase the transfer rate of water into the resin mixture phase in the second step. It is important to reduce the contamination rate. To this end, for the former, it should be noted that in addition to the selection of the organic liquid, various mixing factors that determine the transfer rate of the resin should be optimized using known methods, and for the latter, Care should be taken to select the appropriate separator. Furthermore, in order to prevent resin loss and reduce costs associated with wastewater treatment, it is effective to incorporate a step of recovering the resin and organic liquid remaining in the aqueous phase separated in the second step. As a recovery method, in addition to physical recovery methods such as centrifugation and floating methods using aeration, coagulation-sedimentation methods by adding an aqueous flocculant solution and flotation methods are also effective. In particular, in the flocculation method, the organic liquid emulsion remaining in the aqueous phase is also flocculated together with the resin, so the cake or slurry obtained by separating the resulting aggregates from the aqueous phase contains a considerable amount of plasticizer and organic liquid. Contains (if used). Therefore, it is possible to obtain a resin composition by preferably mixing this cake or slurry with the resin mixture separated in the second step and then drying it. Alternatively, the aggregated and separated product may be returned to the first step. In this collection by flocculation, known flocculants can generally be used,
For example, inorganic flocculants such as aluminum sulfate and polyaluminum chloride, inorganic salts such as sodium chloride,
Polymer flocculants such as polyacrylic acid and polyacrylamide are used. However, since the addition of these flocculants has a negative effect on the quality of the product resin, especially the thermal stability and transparency, their excessive use should be avoided. It should be less than 1 part by weight per part by weight. Next, the present invention will be explained by examples. Example 1 1200 g of an aqueous dispersion of polymerized polyvinyl chloride resin (solids content 44% by weight) for paste processing
When 120 g of di-2-ethylhexyl phthalate and 320 g of n-hexane were placed in a wide-mouthed polyethylene bottle and mixed with shaking for 30 minutes at room temperature (20°C), the main components were resin, plasticizer, and n-hexane. It was separated into a slurry A and an aqueous phase B. Aqueous phase B was collected, and 0.1 g of a 10% aqueous solution of aluminum sulfate 18 hydrate was added thereto at room temperature (20° C.) and stirred, resulting in sedimentation of aggregates. After water was removed by a decanting method, the mixture was centrifuged to sediment using a centrifuge to collect sediment C. A part of A and C are mixed at a weight ratio of 9:1, and the bath temperature is
The mixture was stirred and dried under reduced pressure at 50°C to obtain a granular dry resin composition D. Example 2 300g of the slurry A obtained in Example 1 was placed in a pressure-resistant glass container and dried in a 40°C water bath with stirring and ventilation until the contents became semi-dry. By the way, when I measured the weight of the contents, it was 240g.
It was hot. The contents were extruded as pellets of 2 mm diameter using a manual extrusion type granulator at room temperature (20°C), and then dried in a vacuum dryer at 40°C for 2 hours to obtain 185 g of pellet-like resin composition E. The bulk specific gravity of E is 0.5
g/cc. Comparative Example 1 300 g of the slurry A obtained in Example 1 was placed in a vacuum stirrer, stirred and dried under vacuum at 80° C. for 43 minutes to obtain 183 g of spherical granular composition F. Example 3 Aqueous dispersion of the same resin as used in Example 1 300
g, di-2-ethylhexyl phthalate, 10 g, and carbon tetrachloride, 110 g, were placed in a 500 ml wide-mouthed polyethylene bottle, shaken at room temperature (20°C), and stirred for 30 minutes. The oil phase was separated into two phases using the decanting method. G
and an aqueous phase H. G was dried under reduced pressure in a 5 reduced pressure container equipped with a stirrer while being heated in a 50° C. water bath to obtain 118 g of granular dry resin composition I. Place I in a polyethylene bag, place it between glass plates, place a 1 kg weight on the glass plate, and
When the state of the composition in the polyethylene bag was observed after being left for day and night, it was found that it had almost the same granular shape as before the test, and no blocking had occurred. Example 4 Aqueous dispersion of the same resin used in Example 1
1500 g of dioctyl adipate and 150 g of dioctyl adipate were placed in a 1.8 cylindrical stainless steel mixer equipped with a stirring device consisting of many rod-shaped blades, and heated to room temperature (20°C).
When mixed for 30 minutes at 800 rpm, an aqueous dispersion of a spherical resin composition was obtained. From this aqueous dispersion 42
The spherical resin composition was separated using a mesh wire gauze to obtain 620 g of wet composition J at 40° C. for 2 hours. By vacuum drying J, 480 g of resin composition K was obtained. Comparative Example 2 1000 g of the aqueous dispersion of the resin used in Example 1 was spray-dried using a laboratory spray dryer to obtain a dry resin, and then pulverized twice using a tabletop pulverizer to obtain a dry resin L. Reference Example A portion of the dry resin samples D, E, F, I, K and L obtained in each Example and Comparative Example was extracted with ether, and after measuring the weight percent of the ether extract, the amount remaining after the ether extraction was 100 weight. 60 parts by weight of di-2-ethylhexyl phthalate and 2 parts by weight of T-17MJ (stabilizer made by Katsuta Kako) were mixed for 10 minutes in an Ishikawa-type Raikai machine, and then mixed in an agitator-type vacuum defoaming machine. 5mm
Plastisol was degassed under Hgabs for 10 minutes and various tests were conducted. The results are shown in the table. The test methods and meanings of the numerical values are as follows. (1) Oil absorption: Place 2 g of a dry resin composition sample on a glass plate, knead the sample with a spatula while dropping di-2-ethylhexyl phthalate from a burette, and measure the amount of dripping until the sample becomes putty-like. . (2) Amount of ether extracted A dry resin composition sample is extracted with ether using a Soxhlet extractor for 6 hours, and the amount is calculated from the residue after evaporating the ether. (3) North fineness This indicates the particle size of the resin particles in the sol, and the higher the number, the finer it is (8 is the finest and 0 is the roughest). (4) Viscosity When measured at 6 rpm using a Burtskfield BM type viscometer rotor #4 (first day), and
Sol temperature when left at 23℃ for 7 days (after 7 days)
Values at 23℃. (5) Thermal stability Inject the sol into an aluminum mold,
Changes in color tone at predetermined time intervals in a hot air atmosphere of 190℃ are expressed numerically. 1 (colorless change) to 5 (blackening) (6) Transparency The light transmittance of a film with a thickness of about 370μ obtained by heating the sol at 190℃ for 10 minutes on a 1mm thick glass plate was measured. , the light transmittance of the air
Calculated as 100%. (7) Water whitening resistance The film formed in (6) was soaked in water at 23°C for a day and night, and the light transmittance of the film was measured 10 minutes after the water was removed, and the light transmittance of air was measured.
Calculated as 100%.

[Table] As is clear from the table, the sample of the present invention has a smaller oil absorption amount than the spray-dried product (sample L). That is, it can be made into a sol using a smaller amount of plasticizer, and when it is made into a plastisol, its initial viscosity and aging viscosity are low. In addition, since the resin particles are small when made into a sol (the North Fineness value is large), there are few aggregated particles, the dispersibility in the sol is good, and the final product does not produce streaks or bumps. Further, according to the present invention, since there are few impurities caused by polymerizing agents and the like, a product with excellent thermal stability, transparency, and water resistance can be obtained. It should be noted that the amount of ether extracted from the sample of the present invention was significantly larger than that of the spray-dried product, indicating that plasticizer was incorporated.

Claims (1)

[Scope of Claims] 1. A plasticizer is added to an aqueous dispersion of vinyl chloride resin for paste processing in an amount equal to or less than the same volume as the aqueous dispersion of vinyl chloride resin, and per 100 parts by volume of vinyl chloride resin. After mixing the vinyl chloride resin in a proportion of 15 parts by volume or more to transfer the vinyl chloride resin to the plasticizer phase, separating and removing the aqueous phase, and then drying the phase containing the vinyl chloride resin and the plasticizer. 1. A method for producing a granular vinyl chloride resin composition, which comprises obtaining a granular vinyl chloride resin composition containing a plasticizer, and performing these operations at 70°C or lower. 2 Adding a plasticizer to the aqueous dispersion of vinyl chloride resin for paste processing, the amount used is not more than the same volume as the aqueous dispersion of vinyl chloride resin, and at least 15 parts by volume per 100 parts by volume of vinyl chloride resin. After mixing the vinyl chloride resin in a proportion such that the plasticizer phase is transferred, the aqueous phase is separated and removed, the vinyl chloride resin mixed in the aqueous phase is recovered, and the vinyl chloride resin and plasticizer are combined. A granular vinyl chloride resin composition comprising the steps of: obtaining a plasticizer-containing vinyl chloride resin granular composition by mixing the composition with a phase containing the plasticizer and then drying the composition, and performing these operations at 70°C or lower. Production method. 3 Adding a plasticizer to the aqueous dispersion of vinyl chloride resin for paste processing, the amount used is not more than the same volume as the aqueous dispersion of vinyl chloride resin, and at least 15 parts by volume per 100 parts by volume of vinyl chloride resin. After the vinyl chloride resin is mixed in a proportion such that the plasticizer phase is transferred, the aqueous phase is separated and removed, and the phase containing the vinyl chloride resin and plasticizer is granulated or dried while being granulated. 1. A method for producing a granular vinyl chloride resin composition, which comprises obtaining a granular vinyl chloride resin composition containing a plasticizer by performing the following steps, and performing these operations at 70°C or lower. 4. In the aqueous dispersion of vinyl chloride resin for paste processing, (a) a plasticizer and (b) an organic material that is compatible with the plasticizer, does not substantially dissolve the vinyl chloride resin, and is sparingly soluble in water. Plasticize the vinyl chloride resin by mixing the liquids in a ratio such that the total amount is the same volume or less as the aqueous dispersion of the vinyl chloride resin and 15 parts by volume or more per 100 parts by volume of the vinyl chloride resin. After transferring to the agent phase, the aqueous phase is separated and removed, and then the phase containing the vinyl chloride resin and the plasticizer is dried to recover the plasticizer-containing vinyl chloride resin granular composition, and these operations at 70℃
A method for producing a granular vinyl chloride resin composition, characterized by carrying out the following steps.