JPS646230B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a paste sol containing a plasticizer,
This invention relates to a method for producing vinyl chloride paste resin directly from an aqueous latex. Conventionally, paste sols such as plastisols and organosols have been prepared by once spray-drying and pulverizing an aqueous latex after polymerizing vinyl chloride paste resin to produce a paste resin, and then adding a plasticizer to the resin. According to this method, the solid content concentration of the latex subjected to spray drying after vinyl chloride polymerization is usually 30
~60% by weight, requiring a large amount of water to be evaporated, and since the spray-dried resin was an aggregate, the particle size was large and required pulverization. These steps consume a large amount of energy, contributing to the high cost of paste resin. In addition, in the actual application of paste resin, these paste resins are kneaded with plasticizers, heat stabilizers, and other additives and used as paste sol such as plastisol or organosol. Since it is a fine powder, it tends to form a lot of powder, making it difficult to handle. This dusting problem also occurs in the paste resin manufacturing process, and special equipment is required to ensure safety and health. In short, there were problems in terms of energy conservation and occupational health. As a result of extensive research into a method for producing paste sol directly from latex without going through the spray drying and pulverization steps, the inventors of the present invention have discovered that paste sol can be produced by directly adding a plasticizer to paste resin latex after vinyl chloride polymerization. The resin migrates towards the plasticizer, the water separates and forms two layers, and by adding the plasticizer after the dispersion of the latex is broken down, it separates more quickly into two layers, and then the water separates into two layers. They discovered that a paste sol can be easily obtained by removing the layers, and have arrived at the present invention. That is, an object of the present invention is to provide a method for producing a paste sol directly from latex after vinyl chloride polymerization, without going through spray drying or pulverization steps. Therefore, the gist of the present invention consists of mixing a disrupted aqueous latex dispersion of vinyl chloride paste resin with a plasticizer to transfer the paste resin into the plasticizer phase, and then separating the aqueous phase. It consists in a method for producing a paste sol. The method of the present invention will be explained in detail. The vinyl chloride paste resin latex that can be used in the method of the present invention can be produced by adding vinyl chloride or a mixture of vinyl chloride and a comonomer copolymerizable therewith, such as vinyl acetate, acrylic acid, methyl acrylate, etc., by a conventional emulsion polymerization method or finely divided polymerization. Preferably, the latex is produced by suspension polymerization. The comonomer copolymerizable with vinyl chloride is not limited to the above-mentioned specific examples, and the type of emulsifier or suspending agent used during polymerization is not particularly limited either. In addition, the latex may contain a polymerization aid added before or during the polymerization, a powder filler such as calcium carbonate, etc., as long as it does not adversely affect the paste sol formation described below. The latex may contain various physical property improving aids or processing aids such as lipophilic heat stabilizers, colorants, ultraviolet absorbers, antioxidants, lubricants, and fillers. Although the solid content concentration of the latex varies depending on the bath ratio of the polymerizable monomer and water, additives, and the degree of polymerization, it is preferable to have a higher solid content in consideration of the addition of plasticizer, water separation, the size of the equipment, etc. Usually, it is desirable to use 30% by weight or more of the total latex. The plasticizer used in the method of the present invention is not particularly limited, and may be any of a variety of plasticizers that can be used as plasticizers for vinyl chloride resins. For example, phthalate ester plasticizers such as dibutyl phthalate, diheptyl phthalate, dioctyl phthalate, diisodecyl phthalate, butyl lauryl phthalate, ditridecyl phthalate, butyl benzyl phthalate, butyl phthalyl butyl glycolate, tricresyl phosphate, and phosphoric acid. Phosphate ester plasticizers such as trioctyl, fatty acid ester plasticizers such as tri-n-butyl citrate, dioctyl adipate, dioctyl azelaate, dioctyl sebacate, methyl acetyl ricinoleate, alkyl epoxy stearate, epoxidized soybean oil These plasticizers can be used singly or in combination of two or more. The amount of plasticizer added to the latex varies depending on various conditions such as the method of separating the paste sol from the latex, the separation operation, and the final use of the paste sol, but the amount used is not particularly limited. , based on 100 parts by weight of solids in latex
It is desirable to use 20 parts by weight or more, usually up to 100 parts by weight, preferably up to 50 parts by weight. For example, if you want to take out the paste sol in granular form, add about 20 to 30 parts by weight of plasticizer, and if you want to take out the paste sol in sol form, add 30 parts by weight.
Preferably, 40 parts by weight or more may be used. The amount of plasticizer is 20 parts by weight per 100 parts by weight of solid content in latex.
If the amount is less than 100 parts by weight, it will be difficult to completely transfer the paste resin in the aqueous phase to the plasticizer phase, and if the amount of plasticizer used exceeds 100 parts by weight, the amount to be processed will increase. Otherwise, the resulting paste sol cannot be used in high-concentration fields. Therefore, it is preferable to take out a paste sol with a high concentration of up to about 50 parts by weight of plasticizer and dilute it to an appropriate concentration before use. The method of the present invention involves adding a plasticizer to the above-mentioned latex dispersion system and stirring it, or adding and mixing a plasticizer to the latex and then destroying the latex dispersion system, so that the paste resin becomes a plasticizer phase. Stirring is continued until the paste sol and water are completely separated, and the upper aqueous phase and the lower paste sol phase are separated. The timing of adding the plasticizer to the latex is not particularly limited, but it can be added to the latex after polymerization of the paste resin at any time as described below. In the method of the present invention, in order to speed up the transition of the paste resin to the plasticizer phase, the dispersion system of the vinyl chloride paste resin latex is destroyed and the plasticizer is added after the paste resin is gently agglomerated. is preferable. Methods for destroying the dispersion system of vinyl chloride paste latex include, for example, applying mechanical shearing force such as high-speed stirring, irradiating with ultrasonic waves, etc., heating with steam, etc.
A method of adding an electrolyte such as alum or calcium chloride, a method of adding an acid or alkali such as hydrochloric acid or caustic soda to decompose a dispersant, a method of adding a polymer flocculant such as polyacrylamide, a method of freezing with a cryogen, etc. Various methods are employed. Prior to the destruction of the dispersion system, an auxiliary agent such as an emulsifier may be added in order to maintain the quality of the paste sol. If the latex dispersion system is insufficiently broken, the transfer of the paste resin to the plasticizer phase will be delayed, and in some cases, the aqueous phase may become cloudy with fine particles of the paste resin. Furthermore, when to add plasticizer to latex,
The temperature at which the paste resin in the latex does not quickly absorb the plasticizer, e.g. below 40°C, preferably
It is desirable that the temperature be below 35°C. Addition of plasticizers to latexes at temperatures above 40°C causes rapid absorption of the plasticizer into the paste resin, resulting in an increase in the viscosity of the plasticizer phase or, in extreme cases, gelation. This temperature varies depending on the composition of the paste resin in the applied latex; for example, straight homopolymers with a high degree of polymerization can be treated at temperatures above 40°C, e.g. 50°C; Some polymers or copolymers must be processed at relatively low temperatures, ie, at temperatures below 35°C. Therefore, in the case of the method of the present invention, the temperature of the latex is set at 35°C.
It is almost sufficient to keep it below. In the method of the present invention, it is also possible to use a hydrophobic diluent such as texanol isobutyrate, dodecylbenzene, kerosene, mineral spirits, etc. together with the plasticizer, if necessary. However, if the diluent has low affinity with the paste resin, phase separation may not be successful. Therefore, it is desirable to add a diluent intended for the organosol after the paste sol is separated and taken out. There are no particular restrictions on the speed, time, etc. of stirring after adding the plasticizer to the latex.
This may be continued for several minutes to several tens of minutes until the paste sol phase and aqueous phase are completely separated. Since stirring requires a considerable amount of power, it is preferable to use a stirrer with slightly larger power.
Preferably, a mixing mixer such as that used for conventional plastisol compounding is used. The above-mentioned layer separation under stirring is easy, and after complete separation, the stirring is weakened or the mixture is allowed to stand still, and the upper aqueous phase is removed by decantation or the lower plasticizer phase is extracted to form a paste. Separate and take out the sol. The extracted paste sol is stirred and separated repeatedly by adding pure water as necessary to remove impurities such as emulsifiers, dispersants such as suspending agents, and electrolytes used to destroy the dispersion system. . Since the paste sol thus obtained still contains a considerable amount of water, it is preferable to remove the water through a dehydration step. The dehydration method involves, for example, passing the paste sol through a simple three-roll roll or the like to separate most of the water, and then dehydrating it under reduced pressure. In order to remove water more effectively, a method is also adopted in which a suitable surfactant is added before dehydration by squeezing using three rolls. However, depending on the application,
For example, when used for forming an extremely thin film, the above-mentioned dehydration step can be omitted. In addition, the paste sol produced by the method of the present invention also contains plasticizers, diluents, ultraviolet absorbers, colorants, heat stabilizers, antioxidants, blowing agents,
It goes without saying that additives (materials) used in ordinary paste sol, such as foaming aids and fillers, can be added as appropriate. According to the method for producing paste sol such as plastisol or organosol according to the present invention, vinyl chloride paste resin latex can be made into a sol without spray drying or pulverization, thereby preventing dusting and reducing the large amount of energy previously required. is completely unnecessary, paste sol can be produced at low cost, and has extremely high industrial value in terms of energy saving and occupational health. Since the obtained paste sol is manufactured without going through a drying or pulverizing process, it does not contain hard agglomerated particles, has good heat gelling properties during molding, and has a glossy finish on the resulting molded product. At the same time, there is little discoloration due to heating. In addition, its physical properties are superior to those of conventional paste sol molded products at the same molding temperature. The method of the present invention will be explained below in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 After pre-emulsifying 100 parts by weight of vinyl chloride, 100 parts by weight of water, 1 part by weight of sodium dodecylbenzenesulfonate and 0.15 parts by weight of lauroyl peroxide, polymerization was carried out at 45°C for 20 hours. A portion of the vinyl chloride paste resin latex thus obtained was taken out into a container equipped with a stirrer, and the dispersion system was disrupted using the following various methods. (i) Add 0.5 parts by weight of calcium chloride to 100 parts by weight of solids in the latex. (ii) Stir vigorously using a colloid mill (5000 rpm). (iii) Cool to room temperature after steam heating (100℃). (iv) Externally cool with cryogen and leave at room temperature after freezing. To the latex whose dispersion system has been destroyed by the above method and loose agglomeration has occurred, an amount of plasticizer (a) dioctyl phthalate (b) diisodecyl phthalate (c) is added in an amount equivalent to 40 parts by weight per 100 parts by weight of solid content in the latex. Dioctyl adipate (d), butyl benzyl phthalate (e), dibutyl phthalate (f), and epoxidized soybean oil were respectively added and stirred for 10 minutes. The paste resin transferred to the plasticizer phase and was separated into upper and lower layers.
The upper layer consisted of an almost transparent aqueous phase, and the lower layer was a plasticizer phase to which the paste resin had migrated. Furthermore, floating plasticizer, which has a specific gravity lower than water, was not observed on the liquid surface of the upper layer, and all of the plasticizer was contained in the paste sol layer. The aqueous layer was removed by decantation, and an appropriate amount of water was added twice to repeat the washing process, followed by squeezing and dehydration through three rolls. Most of the water contained in the paste sol layer as water droplets was removed in this process, but this was further dehydrated in a vacuum dryer with a stirrer (at room temperature) to reduce the water content to 1%.
The following paste sol was prepared. Add 3 parts by weight of a heat stabilizer (calcium-zinc type) per 100 parts by weight of the paste sol to the obtained paste sol, and apply it on a glass plate to a thickness of 1 mm.
The samples were allowed to gel for 5 minutes in an oven heated to 200°C, then taken out, and the quality of the surface gloss was visually evaluated, and the results are shown in Table 1. For comparison, a similar paste sol was produced from a paste resin that had been once spray-dried (however, only the plasticizer dioctyl phthalate was used), and evaluated in the same manner as in Example 1. In the evaluation, the comparative example was rated 3rd grade (fair), the better one was 2nd grade, and the better one was 1st grade.

[Table] From the results in Table 1, it appears that the gloss that was exposed to high temperatures before sol formation is slightly inferior, but it is much better than the conventional product (comparative example). Example 2 In a 100 glass lined autoclave,
100 parts by weight of ion-exchanged water and 3 parts by weight of vinyl chloride seed polymer latex having a unit particle size of 0.4 μm and an average degree of polymerization of 1500 were charged as polymer components. after that,
Degas under reduced pressure, add 97 parts by weight of vinyl chloride, and lower the temperature.
Raise the temperature to 50℃ to start the polymerization reaction and
0.015% by weight (based on vinyl chloride) of potassium persulfate and 5 molar equivalent (based on potassium persulfate) of sodium bisulfite were added continuously through separate inlet tubes throughout the entire polymerization time. In addition, from the time the polymerization rate reached 15% by weight until the reaction pressure started to drop, sodium lauryl sulfate was continuously added as an emulsifier at a rate of 0.01% by weight to vinyl chloride per hour to form a vinyl chloride paste resin latex. was manufactured. This latex was cooled to a temperature of 35°C or less, and 40 parts by weight of the plasticizer dioctyl phthalate was added to 100 parts by weight of the solid content of the latex. A paste sol was produced. The surface gloss was rated as grade 1. Example 3 A latex was produced in the same manner as in Example 1, except that in the method for producing vinyl chloride paste resin latex of Example 1, 100 parts by weight of vinyl chloride was replaced with a mixture of 95 parts by weight of vinyl chloride and 5 parts by weight of vinyl acetate. was manufactured. After cooling the latex to a temperature of 35°C or less, add 40 parts by weight of dioctyl phthalate per 100 parts by weight of solid content in the latex, and produce a paste sol with a moisture content of 1% or less in the same manner as in Example 1 (i). did. The surface gloss was rated as grade 1.

Claims (1)

[Scope of Claims] 1. A paste sol comprising a broken aqueous latex dispersion of vinyl chloride paste resin mixed with a plasticizer to transfer the paste resin to the plasticizer phase, and then separating the aqueous phase. manufacturing method. 2 The temperature of the dispersion system of latex is
A method for producing a paste sol according to claim 1, wherein the temperature is 40°C or less. 3. Claim 1 or 2, in which a plasticizer is added and mixed after the latex dispersion system is destroyed.
2. Method for producing paste sol described in Section 1. 4. The method for producing a paste sol according to claim 1 or 2, wherein the latex dispersion system is destroyed after adding the plasticizer.