JPH069793A - Process for molding plastic material - Google Patents

Abstract

PURPOSE:To decrease the no. of steps up to the step of producing a molded product using a molding material comprising waste coating material and a polyolefin resin and to improve the strength of the molded product over that of the conventional molded products wherein use is made of particles of waste coating material. CONSTITUTION:The mixing step of mixing a waste coating material contg. an uncured thermosetting resin with a polyolefin resin to prepare a molding material is followed by the step of forming a molded item from the molding material and the step of reacting the thermosetting resin contained in the molded item. The reaction of the uncured resin after formation of the molded item improves the strength of a final molded product because of entanglement of resin molecules on the molecular level thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molding method, and more particularly to a plastic molding method using a molding material containing paint waste.

[0002]

2. Description of the Related Art During spray coating, not all of the paint mist sprayed from a coating gun adheres to the object to be coated, but a considerable amount of it scatters around. The paint mist scattered around is collected in the circulating water in the washing booth and separated from the water in the treatment tank to become paint waste. This paint waste is a mixture of various substances such as resins, pigments, solvents and water in various proportions, and since it is difficult to reuse it as paint anymore, it is currently incinerated. .

However, even in the incineration process, unburned harmful gas or offensive odor may be generated. There is also a problem that the furnace is corroded by acid gas generated during combustion. Furthermore, the amount of paint waste generated in daily painting work is enormous, which is a waste of resources. Therefore, the reuse of paint waste was examined, and JP-A-53-61627 and JP-A-55-1 were used.
Japanese Patent No. 8450 and the like disclose powdering into a filler such as a polyolefin resin. For example
In 55-18450, the paint waste is crushed to about 150 μm.
Powders heat-treated at 150 to 300 ° C as described below are mixed in a polyolefin resin and used as a molding material.

[0004]

However, in the above-mentioned method of recycling paint waste, it is necessary to regulate the particle size of the powder obtained from the paint waste to about 150 μm or less, and there are two steps of pulverization and classification. Was required, and the man-hour was enormous. This is because when the particle size of the powder becomes large, the surface of the molded body becomes rough and smooth skin cannot be obtained.

There is also a problem that the tensile strength and the bending strength of the molded body formed from the coating waste powder decrease as the mixing amount of the coating waste powder increases. The present invention has been made in view of such circumstances, and when using a polyolefin resin mixed with paint waste as a molding material, the man-hours until molding are reduced, and the strength of the obtained molded body is reduced to the conventional one. It is intended to improve the quality of the molded product using paint waste powder.

[0006]

A plastic molding method of the present invention for solving the above problems comprises a mixing step of mixing a paint waste containing an uncured thermosetting resin with a polyolefin resin to form a molding material, and It is characterized by comprising a molding step of forming a molded body from a molding material and a reaction step of reacting a thermosetting resin contained in the molded body.

In the mixing step, the paint waste and the polyolefin resin are mixed. As the paint waste, water and solvent are removed and pulverized so as to be easily mixed with the polyolefin resin. For example, put what is separated from water into a sealable processing tank that has crushing blades, and dry /
What was crushed can be used. If the pulverized paint waste is left as it is, the uncured resin adheres to each other to form a large soft lump, so that it is mixed with the polyolefin resin while the pulverized state is maintained.

Polyolefin resin is polypropylene,
Polyethylene, ethylene propylene copolymer, etc. are used. As for the shape, it is preferable to use a powdery one that is easily mixed. Since the powdered polyolefin resin adheres to the surface of the pulverized product of the paint waste, it is possible to prevent the pulverized products from sticking to each other and maintain a desirable granular state as a molding material for a long period of time.

From the viewpoint of performance, the mixing ratio of the paint waste and the polyolefin resin is preferably as much as the polyolefin resin is, but if the paint waste does not exceed 50% by weight, it has sufficient physical properties as a molded product. ing. In particular, it has been clarified that when the amount is 30% by weight or less, the bending strength is improved as compared with a pure polyolefin molded body in which paint waste is not mixed.

The molding step is a step of molding the above molding material to form a molded body. When heated, the uncured resin in the paint waste reacts and exists as foreign matter in the molded body, so molding methods such as extrusion molding that hold the molding material in the molten state for a long time cannot be used. , Hot press molding is mainly used. In some cases, injection molding can also be used.

The most characteristic reaction step of the present invention is a step of reacting the uncured thermosetting resin in the obtained molded body. For example, the reaction can be carried out by heating and holding in a mold. For example, in the case of hot press molding, a mold temperature of 180 to 200 ° C., a pressing pressure of 50 to 200 kg / cm ² , and a pressing time of about 3 to 5 minutes can be performed simultaneously with the molding. In addition, in the case of injection molding, after injection into the mold, heating and holding can be performed for reaction. In addition, when heating and holding in the mold, it is necessary to perform degassing from time to time.

It is also possible to react by heating after taking out the molded product from the mold. In this case, it is necessary to carry out at a temperature at which the shape of the molded body can be maintained. Furthermore, the reaction can be caused by irradiating the molded body with ultraviolet rays or far infrared rays. For example, when irradiating ultraviolet rays,
Using a near-ultraviolet lamp of 400 nm, if the ambient temperature is about 60 ° C, it will be 3 hours or more.
Irradiation for about 60 minutes is required. It is considered that the irradiation of ultraviolet rays markedly improves the bending strength, which is caused by the decomposition and excitation of a part of the components in the molded body to activate the reaction and the reaction of the polyolefin resin.

[0013]

In the plastic molding method of the present invention, the pulverized paint waste is first mixed with the polyolefin resin in the mixing step to form a molding material. When this molding material is used, the uncured resin in the pulverized product of the paint waste is momentarily melted together with the polyolefin resin during thermoforming, so that a molded product having a smooth surface can be obtained even if the pulverized product has a slightly large particle size.

In the obtained molded body, at least the uncured resin contained therein is cured in the reaction step. Therefore, unlike the conventional molded product that uses the already-cured paint waste powder as the filler, the uncured resin cures in a state in which it is entangled with the polyolefin resin at the molecular level due to melting during the above-mentioned molding, and therefore the cross-linking structure is complicated Turn into. As a result, the strength is improved as compared with the conventional molded body containing the paint waste.

[0015]

Therefore, according to the molding method of the present invention,
It eliminates the troublesome process of finely pulverizing paint waste and classifying it, which can reduce man-hours and improve productivity. This can significantly reduce the cost. Further, the obtained molded body has higher strength than that obtained by the conventional method. This expands the uses of the molded body. Further, in the case of forming a molded product having the same level of strength as the conventional one, the content of the paint waste can be increased more than in the conventional one. As a result, the efficiency of recycling the paint waste can be improved, and the waste of limited resources can be further prevented.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples. [Example 1] 6 kg of paint waste accumulated in the coating circulating water pit of an automobile body intermediate coating line was charged into a 20-liter capacity treatment tank having a crushing blade and crushed by a rotary blade while heating with steam. Then, it was strained with a 9-mesh wire mesh to obtain paint waste powder with a particle size of 2 mm or less. The properties of this paint waste powder are shown in Table 1.

[0017]

[Table 1] (1) Mixing Step The above paint waste powder and polyethylene pellets (manufactured by Sumitomo Chemical Co., Ltd.) were put into a treatment tank having a rotary blade and mixed until uniform. The mixing ratio was such that the paint waste powder was 0, 10, 20, 30, 50% by weight, and 5 types of molding materials were obtained. (2) Molding process / reaction process Weigh 130 g of each of these molding materials, fill each mold, and perform hot press molding under the conditions of mold temperature 190 ℃, press pressure 100 kg / cm ³ , press time 3 minutes. , 150 × 70
A flat test piece of × 10 mm was formed. Maximum particle size
Despite the use of the 2 mm molding material, the surface of the test piece was smooth and the surface roughness was extremely small. (3) Test Tensile strength and bending strength were measured for each of the obtained test pieces. The test method was based on JISK6301. The results are shown in FIGS. 1 and 2. Comparative Example 1 The paint waste powder of Example 1 was heat treated in a constant temperature hot air drying oven at 150 ° C. for 4 hours. Table 2 shows the properties of this heat-treated powder.

[0018]

[Table 2] The heat-treated powder is strained with a 100-mesh wire mesh to reduce the particle size.
A test piece was prepared in the same manner as in the example except that the particle size was 140 μm or less and the material was mixed with polyethylene pellets to obtain a molding material. Then, the same test as in Example 1 was conducted, and the results are shown in FIGS. 1 and 2. [Evaluation] From FIGS. 1 and 2, it is clear that the test piece formed by the method of Example 1 is superior to the one formed in Comparative Example 1 in strength. Further, regarding the bending strength, when the paint waste powder is 30% by weight or less, excellent results are shown as compared with the case where the paint waste powder is not added. [Example 2] The same coating waste powder as in Example 1 was used, and mixed with polypropylene powder (Showa Denko KK) to obtain a molding material of Example 2. The mixing ratio is 30% by weight of paint waste powder. And mold temperature 200 ℃,
Hot press molding was performed under the conditions of a press pressure of 200 kg / cm ² and a press time of 5 minutes. Tensile strength, elongation, bending strength, IZOD impact strength and heat distortion temperature of the obtained test piece were measured, and the results are shown in Table 3. The obtained test piece was irradiated with near-ultraviolet light having a wavelength of 200 to 400 nm for 120 hours, and the same test was performed. [Comparative Example 2 / Comparative Example 3] A polypropylene material alone was used as the molding material, and a calcium carbonate powder mixed with polypropylene pellets in an amount of 30% by weight was used as the molding material. And the test piece of the comparative example 3 was formed. Then, the same test as in Example 2 was performed, and the results are shown in Table 3. The test method conformed to JIS K6301.

[0019]

[Table 3] [Evaluation] From Table 3, the test piece of Example 2 has the same bending strength as Comparative Example 2 without being irradiated with ultraviolet rays, but the bending strength is remarkably improved by irradiation of ultraviolet rays. I understand. In addition, other physical properties are also improved by irradiation with ultraviolet rays. This is because the crosslink density was improved by the irradiation of ultraviolet rays, and it is speculated that polypropylene is also involved in the crosslink reaction.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the mixing ratio of paint waste powder and bending strength in Examples.

FIG. 2 is a graph showing the relationship between the mixing ratio of paint waste powder and tensile strength in Examples.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technology display location B29K 101: 10 (72) Inventor Toshiyuki Otsubo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd. (72) Inventor Yuji Ishihara 6-1, Meiwa-cho, Toyota-shi, Aichi Toyota Chemicals Co., Ltd. (72) Inventor Sumio Okada 6-cho, Toyota-shi, Aichi Kyoho Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A mixing step of mixing a waste paint containing an uncured thermosetting resin with a polyolefin resin to obtain a molding material, a molding step of forming a molding from the molding material, and And a reaction step of reacting the thermosetting resin contained therein.