JPH05309788A - Polypropylene lining and lining powder - Google Patents

Abstract

PURPOSE:To provide polypropylene lining and a lining powder. CONSTITUTION:The polypropylene lining of a metal is composed of a heated molten matter wherein a polypropylene/polyethylene wt. ratio is 50/1-1/1. A powder for polypropylene lining is obtained by mixing a polypropylene powder and a polyethylene powder both of which have a mean particle size of 500mum or less in a wt. ratio of 50/1-1/1 or mixing polypropylene and polyethylene in a wt. ratio of 50/1-1/1 to melt and knead both of them and grinding the resulting kneaded mixture to obtain a powder with a mean particle size of 500mum or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-melting polypropylene lining and a powder for lining which are applied to metal (carbon steel) materials such as flue gas desulfurization equipment, gas purification plants, seawater desalination equipment, and thermal power plants.

[0002]

2. Description of the Related Art Conventional polypropylene linings have a polypropylene sheet or pipe surface that has been treated with corona discharge, a mixture of concentrated sulfuric acid and chromic acid to provide adhesion, and then coated with an adhesive such as epoxy resin. So-called sheet lining is known to be used for adhesion, but like polyethylene and fluororesin, polypropylene powder is sprinkled on the surface of the material to be lined that has been heated above the melting temperature of polypropylene, and then fused to form a film. No so-called hot melt polypropylene lining has been proposed. Further, there is no commercially available lining powder for spraying the powder to heat-melt polypropylene lining, and there is no proposal case.

[0003]

The polypropylene lining in which the sheet or pipe is surface-treated and adhered with an adhesive for lining has the following problems.
It is rarely applied industrially. (1) It is a method of applying and pasting an adhesive, and defects such as defective adhesion are likely to occur. (2) Adhesion method, in which similar to rubber lining, it is pressed manually to be bonded, or it is pressed with an appropriate tool to be bonded, so that it has a complicated shape such as a vent part of a pipe, a T-shaped pipe or a pipe with a small diameter It is difficult to apply to (3) In the case of lining pipes, polypropylene pipes extruded by an extruder are used in advance. Therefore, in plants where pipes of various pipe diameters are used, polypropylene pipes suitable for those pipe diameters are manufactured. Molds are needed to make the pipes, which makes polypropylene pipes very expensive.

Generally, polypropylene is used for injection molded products, extrusion molded products, films and the like. Commercially available polypropylene adheres to a metal surface in a heating and melting state, but peels off upon cooling and solidification. I will end up. Therefore, as described above, the polypropylene lining has been put into practical use only by subjecting an extruded sheet or pipe to various surface treatments to impart adhesiveness and adhesively lining with an adhesive.

The reason why commercially available polypropylene cannot be adhered to a metal by the heating and melting method is that polypropylene has a large solidification shrinkage and the solidification shrinkage continues for a long time even at a relatively low temperature (normal temperature). The stress is considerably larger than polyethylene and fluororesin,
Alternatively, it is considered to be due to the influence of additives such as lubricants added to improve the releasability in injection molding, extrusion molding, etc., but the detailed factors are unknown.

In view of the above technical level, the present invention intends to provide a hot-melt lining material which retains excellent chemical resistance, heat resistance and mechanical properties of polypropylene and has excellent adhesiveness, and a powder for the lining. It is what

[0007]

Means for Solving the Problems The inventors of the present invention have made earnest experiments and studies to develop a heat-melting polypropylene lining using powder capable of dealing with complicated shapes and large and small tube diameters. In contrast to peeling during cooling and solidification, it was found that by mixing polyethylene with polypropylene at an appropriate ratio, a good lining coating with strong adhesion can be obtained without peeling, and the present invention is based on this finding. Has been completed.

That is, according to the present invention, (1) the weight ratio of polypropylene / polyethylene is 50 /
A metal polypropylene lining, characterized in that it consists of a heat melt of 1 to 1/1. (2) A polypropylene lining powder, characterized in that polypropylene powder having an average particle size of 500 μm or less and polyethylene powder are mixed in a weight ratio of 50/1 to 1/1. (3) Polypropylene / polyethylene weight ratio is 50 /
A polypropylene lining powder, which is obtained by melt-kneading a mixture of 1 to 1/1 and then pulverizing the mixture so as to have an average particle size of 500 μm or less.
Is.

The metal targeted by the present invention is generally carbon steel.

The mixing ratio of polypropylene and polyethylene in the present invention varies depending on the type and grade of polypropylene and polyethylene used, but an appropriate range is 50.
It is / 1-1 / 1. If the mixing ratio of polyethylene is too large, the softening point and heat resistance will be close to those of polyethylene.

Further, if the particle size of the powder suitable for the heat melting lining is 500 μm or less, a film having a uniform film thickness can be obtained, but the average particle size is preferably 100 to 150 μm. A lining film can be formed even when a powder having an average particle size of more than 500 μm is used, but not only it takes a long time to melt to form the film, but also the surface becomes uneven and a lining film having a uniform film thickness is formed. become unable.

[0012]

In the lining material of the present invention, the weight ratio of polypropylene to polyethylene is 50/1 to 1/1, but both polypropylene and polyethylene are melted in the heat-melted state, and the polyethylene is melted when cooled and solidified. Since polypropylene and polypropylene have different flow characteristics and solidification temperatures, polypropylene solidifies at a higher temperature than polyethylene. Therefore, the polypropylene is solidified in a state of being dispersed in polyethylene, and the polyethylene is mainly adhered to the metal (carbon steel) surface although the polypropylene is large. Polyethylene is a crystalline polymer and its solidification shrinkage is almost the same as that of polypropylene, but polyethylene lining has been put into practical use without peeling during solidification because the creep deformation stress of polyethylene is very small. The polyethylene is stretched at the time of solidification and contraction, and the stress is instantly relaxed to a stress smaller than the adhesive force, so that a lining that is not peeled off can be obtained. In the lining material of the present invention, polyethylene adheres to the metal surface, so that the lining without peeling can be obtained by the above-described action.

Therefore, in the lining powder for obtaining the lining of the present invention, the mixing ratio of polyethylene to polypropylene can be reduced to 50/1 by mixing polypropylene and polyethylene having a small particle size. When it is applied to an environment in which the ratio of (1) may be large (when polyethylene is used in contact with a liquid of 60 to 70 ° C. in an environment where the use limit temperature is 60 ° C. or higher), the mixing ratio of 1/1 is sufficient.

Further, the powder for lining is melt-kneaded by using a melt-kneader and then pulverized to have an average particle size of 500 μm or less. The mixing is uniform and a lining with better adhesion is obtained.

[0015]

[Examples] Polypropylene pellets having a melt flow index (MI) of 5 and polyethylene pellets having an MI of 5 were pulverized with a freeze pulverizer using liquid nitrogen, and then sieved into powders having an average particle diameter of 1000 µm, 500 µm, and 100 µm. After that, a lining powder was obtained by mixing the polypropylene powder and the polyethylene powder in the compounding ratio shown in Table A. After mixing the polypropylene and polyethylene pellets in the blending amounts shown in Table A, the mixture was kneaded using a melt kneader and then pulverized by a freeze pulverizer and sieved to obtain an average particle diameter of 1000 μm, 500 μm, 100 μm. A lining powder was obtained.

Next, length 70 mm x width 200 mm x thickness 5 mm
After degreasing the carbon steel sheet of No. 1, shot blasting, heating this on a heating hot plate so that the surface temperature becomes 250 ° C. ± 20 ° C., sprinkling the powder, heating and melting lining, and film thickness 1. A 5 mm lining steel plate was obtained. after that,
The adhesive strength was determined by a 90 ° peeling method with a width of 10 mm, and a durability test was conducted for 6 months under the conditions of 5% H ₂ SO ₄ and 100 ° C. The results are shown in Table A.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

EFFECTS OF THE INVENTION According to the present invention, it is possible to apply up to a high temperature range which cannot be applied with conventional polyethylene lining and rubber lining, and it has excellent heat resistance and chemical resistance. It is possible to provide a hot-melt polypropylene lining material using a powder applicable to the above and a powder for the lining. Up to now, expensive high-grade stainless steel or expensive fluororesin-based lining material has been applied to equipment with a severe corrosive environment in a high temperature range where polyethylene lining and rubber lining cannot be applied. Compared with the above, polypropylene and polyethylene, which are much cheaper than the above, are used as raw materials, and a very inexpensive lining material can be provided. From the above results, its industrial and economic value is very large.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area C09D 123/10 PEQ 7107-4J

Claims (3)

[Claims] 1. A metal polypropylene lining, characterized in that it comprises a hot melt having a polypropylene / polyethylene weight ratio of 50/1 to 1/1. 2. A polypropylene powder having an average particle diameter of 500 μm or less and a polyethylene powder in a weight ratio of 50/1 to 1
Powder for polypropylene lining, characterized by being mixed in a ratio of / 1. 3. A polypropylene / polyethylene mixture having a weight ratio of 50/1 to 1/1, melt-kneaded, and then pulverized to have an average particle size of 500 μm or less. Powder for polypropylene lining.