JPH0329099B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is based on polyvinyl chloride resin (hereinafter referred to as PVC) for sintering.
The present invention relates to a method for producing a composition, and more specifically to a method for producing a PVC composition for sintering that has a uniformly dispersed stabilizer and has excellent thermal stability. Conventionally, the method of directly heating and molding powdered resin has been widely used for thermosetting resins such as phenolic resin and thermoplastic resins such as polyethylene, but for PVC, the raw material supply form is powder. However, coating film formation using the fluidized dipping method using PVC for paste has only been carried out in a limited number of areas. This is because in the case of hard PVC, high heat and high pressure must be applied to fuse the particles, which not only causes thermal decomposition of the PVC and decreases productivity, but also deteriorates the physical properties of the resulting molded product. This is because it is extremely low. In addition, if PVC with a low degree of polymerization is copolymerized with vinyl acetate or other low softening point PVC, and if a large amount of plasticizer is added, the melt flowability during heating will naturally be improved, and the heating and processing of the powder will improve. Sintering by pressure etc. becomes possible. However, since mechanical kneading is not performed in the sintering of PVC powder, the dispersion of the stabilizer tends to be non-uniform, and therefore thermal stability during hot molding becomes a problem. Therefore, in order to improve thermal stability, it is important to disperse the stabilizer as uniformly as possible, and for this reason, a method is generally used to prevent poor dispersion by using a liquid stabilizer. However, liquid stabilizers
It is said that it is preferable to use a stabilizer with a high melting point because it is disadvantageous in terms of odor, volatility, heat aging, etc. Therefore, the inventor developed a sintering material with excellent thermal stability.
In order to obtain a PVC composition, we have repeatedly investigated ways to more uniformly disperse a stabilizer with a high melting point. By mixing the stabilizer as a specific dispersion into PVC at a specific temperature, it is possible to achieve the desired purpose. The inventors have discovered that this can be achieved and have arrived at the present invention. That is, the present invention, when producing a sintering composition by adding and mixing a solid stabilizer and a plasticizer to PVC powder, uses the stabilizer as a plasticizer dispersion in which the average particle size is adjusted to be 30μ or less. The present invention provides a method for producing a PVC composition for sintering, which is characterized in that it is added to and mixed with PVC powder. The PVC powder used as a component of the sintering composition in the present invention is a homopolymer of vinyl chloride or 50% by weight or more of vinyl chloride and other copolymerizable monomers, such as vinyl acetate, ethylene, etc. %
It is a powder of a copolymer with: these
A mixture of PVC and other synthetic resins, PVC
Powdered resin mixtures with a fraction of 50% or more by weight can likewise be used. The degree of polymerization of PVC is not particularly limited and may be selected depending on the sintering conditions or usage conditions of the composition of the present invention, but the average degree of polymerization used is usually about 500 to 1500, preferably about 700 to 1000. It's easy to do. In addition, the particle size and particle size distribution of the powder are not limited, and are usually 40 to 300.
A mesh of 80 to 200 mesh is easy to use. In the present invention, a general plasticizer for PVC is used as one component of the sinterable composition. Specific examples include phthalic acid esters such as dioctyl phthalate and dibutyl phthalate, adipic acid esters such as dioctyl adipate and dibutyl adipate, phosphoric acid esters such as tricresyl phosphate, oleic acid, and trimellitic acid. , higher alcohol esters of organic acids such as sebacic acid, and the like. The amount of plasticizer added is usually 30 to 100 parts by weight (PHR) of PVC.
It is 130PHR. If it is less than 30 PHR, it is necessary to raise the sintering temperature, which is undesirable due to problems with the thermal stability of the resin, and if it exceeds 130 PHR, problems such as agglomeration or blocking of the composition will occur when the ingredients are mixed and stirred. In short, the method for preparing a dispersion of a solid stabilizer in a plasticizer in the present invention is such that the average particle size of the stabilizer is
There are no particular limitations as long as the method results in a thickness of 30μ or less, preferably 15μ or less. For example, the solid stabilizer and plasticizer are mixed in advance using a ribbon blender, butterfly mixer, etc. and forcedly dispersed using an ink mill, or the stabilizer is pulverized using a hammer mill, jet mill, ball mill, roller mill, etc., and then mixed in a mixer. A method such as mixing with a plasticizer and forcibly dispersing it with an ink mill can be adopted. Even if the stabilizer is added to PVC in the form of a dispersion with an average particle size of more than 30μ, the effect of improving thermal stability is poor because uniform dispersion is insufficient. The solid stabilizer is not particularly limited as long as it is used for ordinary PVC, and examples include lithium stearate, magnesium stearate, aluminum stearate, calcium stearate, calcium laurate, barium stearate, barium laurate, and zinc stearate. , metallic soaps such as cadmium stearate, lead stearate, and dibasic lead stearate; inorganic acid salts such as tribasic lead sulfate, basic lead sulfite, and dibasic lead phosphite; dibutyltin malate, octyltin malate,
Examples include organic tin compounds such as dibutyltin mercaptide and polymerized organic tin compounds; and composite stabilizers in which two or more types are combined. The type of plasticizer used as a dispersion medium for the stabilizer is not limited, but from the point of view of uniform dispersibility,
The same plasticizers as those used as components of the PVC composition are preferred, specific examples of which are listed above. The concentration of stabilizer in the plasticizer dispersion is usually between 5 and 90
% by weight. If it exceeds 90% by weight, the viscosity will increase and homogeneous dispersion into the plasticizer will be incomplete, and if it is less than 5% by weight, the viscosity of the dispersion will be low, making it difficult to grind with an ink mill, and the stabilizer will separate and coagulate, resulting in poor dispersion. As a result, thermal stability decreases. Addition of the resulting stabilizer dispersion to the PVC is usually carried out before addition of the plasticizer. The number of parts added is usually 1 to 1 as the amount of stabilizer per 100 PHR of PVC.
It is about 10 PHR, preferably about 1.5 to 5 PHR. Also,
The temperature at which this dispersion is added to PVC needs to be below the melting point of the stabilizer. When the melting point is exceeded
The absorption of the stabilizer into PVC is too rapid, causing local unevenness and making uniform dispersion difficult. However, when adding a plasticizer after the stabilizer dispersion is uniformly dispersed in PVC, it is preferable to maintain the temperature at a temperature that does not cause aggregation or blocking of the composition, generally 80° C. or higher. Below this temperature, the stabilizer and the plasticizer are not easily absorbed into the PVC, so the effect of improving thermal stability is small. Further, the stabilizer dispersion and the plasticizer are added and mixed to the PVC using a conventional mixer such as a Henschel mixer or a ribbon blender. The mixing time varies depending on the rotation speed, temperature, and mechanical conditions, but is usually about 5 to 60 minutes. In addition to PVC, the stabilizer dispersion, and the plasticizer, it is of course possible to use ordinary fillers, flame retardants, anti-aging agents, ultraviolet absorbers, stabilizing aids, pigments, etc. as desired. The method of sintering the composition of the present invention obtained in this way is not particularly limited. (3) Forming a laminated sheet by spreading the composition on felt and melting it through a heating furnace; (4) Directly heating the composition. Various molding methods can be applied, such as molding a molded article by spraying the powder onto a mold. It should be noted that sintering can be performed without applying pressure, but if a smooth surface, embossed pattern, etc. are required, a slight amount of pressure may be sufficient. It is also possible to lower the molding temperature and shorten the melting time.
The molding conditions are usually 150 to 300° C. and several seconds to 20 minutes, and are selected depending on the shape of the molded product, the meltability of the composition, etc. When molded at temperatures exceeding 300℃,
Problems may arise with the thermal stability of PVC. The present invention will be explained below based on Examples. Note that the parts and percentages of the ingredients are based on weight. Example 1 A barium stearate/zinc stearate (70/30) composite stabilizer with an average particle size of 75μ was charged into a butterfly mixer, and then stabilizer concentrations of 10, 20 and
After adding and mixing dioctyl phthalate to give a concentration of 50%, the mixture was taken out, and the stabilizer was crushed in an ink mill at 50 to 60°C and mixed to obtain a paste-like dispersion. The particle size of the stabilizer at this time was adjusted by the number of times the ink was passed through the ink mill. Next, 100 parts of polyvinyl chloride (average degree of polymerization 700),
3 parts of the stabilizer dispersion obtained above as a stabilizer and 5 parts of epoxidized soybean oil were mixed and stirred in a 20 Henschel mixer at 30°C, and when the temperature was raised to 100°C, 60 parts of dioctyl phthalate was added. A PVC composition was obtained by gradually adding the mixture, raising the temperature to 120°C, and then cooling it to 50°C. This composition was spread on a 2 mm aluminum plate, adjusted to a thickness of 2 mm using a doctor blade, and sintered in an oven at 230°C for 10 minutes, and thermal stability was evaluated by the number of black spots generated in 5 cm ² . The results are shown in Table 1. In addition,
The results when the stabilizer is not a plasticizer dispersion (experiment numbers 7 and 8) are also shown.

[Table]
Example 2 Tribasic lead sulfate as a stabilizer and trimellitic acid ester as a plasticizer (Adeka Argus Chemical Co., Ltd.)
The same experiment as in Example 1 was conducted except that Adekasizer C-8 (manufactured by Adekasizer C-8) was used. The results are shown in Table 2.

[Table]

Claims (1)

[Claims] 1. When producing a sintering composition by adding and mixing a solid stabilizer and a plasticizer to vinyl chloride resin powder, the stabilizer is chlorinated as a plasticizer dispersion adjusted to have an average particle size of 30μ or less. A method for producing a vinyl chloride resin composition for sintering, which comprises adding and mixing it to vinyl resin powder.