JP2533540B2 - Adhesive powder polyethylene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to powder polyethylene for paints having good adhesiveness, and more specifically, for powder coating methods such as fluidized dipping method and electrostatic coating method. The present invention relates to an adhesive powder polyethylene suitable as such.

[Prior Art] A fluid immersion coating method is known in which a resin powder or the like is fluidized in a fluidized bed, and a preheated metal or the like is dipped in the fluidized bed for coating.

As properties required for application to applications such as coating, it is said that the powder particle shape does not have a fibrous beard, has an appropriate particle size, and has a large density. Adhesive powdered polyethylene, which is used in anticorrosion coating materials for metal materials such as steel as a powder used in such a fluid immersion coating method, has a melt index (MI) of 10 to 30 as its base resin and a density of Linear low density polyethylene (LLDPE) with a grain size of 0.928 to 0.935 and a mesh size of 50 mesh is used.

[Problems to be Solved by the Invention] However, when the linear low-density polyethylene having the above-mentioned characteristics that has been conventionally used is coated by a fluid immersion coating method, a decrease in tensile strength and elongation is observed, In addition, there is a problem that the coating film may break when the coating is peeled off.

[Means for Solving Problems] Therefore, as a result of various studies, the present inventors have found that a linear low-density polyethylene that is a base resin has a melt index of 5 to 50 g / 10 minutes and a density of 0.910 to 0.925 g / By using a linear low-density polyethylene (cm ³ ) modified with unsaturated fatty acids and / or their acid anhydrides as a coating material, a coating with better film strength than the conventional case can be applied. They have found that they can obtain it, and arrived at the present invention.

That is, according to the present invention, the melt index is 5 to 50.
g / 10 min, linear low density polyethylene with a density of 0.910 to 0.925 g / cm ³ modified with unsaturated fatty acids and / or their acid anhydrides, the particle size of which passes through a 30 mesh sieve An adhesive powder polyethylene for painting is provided.

In the adhesive powder polyethylene for coating according to the present invention, its melt index needs to be 5 to 50 g / 10 minutes. If the melt index is less than 5g / 10 minutes, the melt viscosity will be high when the powder is fluidized and dipped, and the coating will not be finished properly.

Also, the density of this adhesive powder polyethylene for coating is
Range of 0.910 to 0.925 g / cm ³ , preferably 0.915 to 0.923 g / c
Must be in the m ³ range. If the density exceeds 0.925 g / cm ³ , the strength of the coating film will decrease, and if it is less than 0.910 g / cm ³ , the rubber elasticity will be so strong that it cannot be used as a fluid immersion powder.

The density of adhesive powder polyethylene for coating is JISK
Measured according to 6760.

The adhesive powder polyethylene for coating has a particle size of 30-mesh sieve, preferably 50-mesh sieve. If the particle size of the adhesive powder polyethylene for coating is larger than that of a 30-mesh sieve, the coating film may not be finished smoothly or pinholes may occur.

The linear low density polyethylene (LLDPE) of the present invention means ethylene and α-selected from the group consisting of butene-1, hexene-1, 4-methylpentene-1 and octene-1.
It is a copolymer with 1 to 10% of olefins. LLDPE is manufactured by the low pressure method. Compared to low-density polyethylene produced by conventional high-pressure method, LLDPE is structurally multi-branched with high-branched low-density polyethylene, whereas LLDPE is linear. There is something.

The adhesive powder polyethylene for coating of the present invention can be produced by the following known pulverization method.

In general, polyethylene is rich in toughness and difficult to crush, so use an impact crusher such as a swing hammer mill or turbo mill, and crush it with liquid nitrogen etc. to prevent melting of polyethylene due to localized heat generation during crushing. Powdered polyethylene can be produced by a method such as cooling a machine or polyethylene.

The polyethylene used in the present invention is preferably modified polyethylene. As the one used for the modification treatment, monobasic unsaturated fatty acids, unsaturated fatty acids such as dibasic unsaturated fatty acids, and acid anhydrides thereof are preferable,
Examples of monobasic unsaturated fatty acids include acrylic acid and methacrylic acid, examples of dibasic unsaturated fatty acids include maleic acid and itaconic acid, and examples of acid anhydrides include maleic anhydride and hymic acid anhydride.

As a method for producing the modified polyethylene, various known methods (eg, solution method, suspension method, melting method) can be adopted.

When the modification treatment is carried out by the solution method, modified polyethylene can be obtained by adding polyethylene, maleic anhydride and the like to a nonpolar organic solvent, adding a radical initiator and heating at high temperature. At this time, the nonpolar organic solvent used is hexane,
Examples thereof include benzene and toluene, and examples of the radical initiator include organic peroxides such as 2,5-dimethyl-2,5-di (tertiary butylperoxy) hexane and benzoyl peroxide. The treatment temperature is a temperature at which polyethylene is dissolved and is usually 110 to 160 ° C.

In the case of modification treatment by the suspension method, polyethylene and maleic anhydride described above are put into a polar solvent (generally water), and a radical initiator is further added and treated at a temperature of 100 ° C or higher under high pressure. Obtained by

Further, when the modification treatment is carried out by the melting method, it can be obtained by carrying out the processing while melt-kneading the polyethylene, the above-mentioned maleic anhydride and the like, and the radical initiator using a melt-kneading machine (for example, an extruder). The kneading temperature varies depending on the kind of the radical initiator used, but is a temperature of not lower than the melting point of polyethylene and not higher than 300 ° C, and generally 120 to 270 ° C.

Examples of the metallic material coated by the method of the present invention include titanium, aluminum, nickel, steel, iron such as stainless steel, copper, zinc, and the like, and alloys thereof.

EXAMPLES Next, the present invention will be described in more detail based on examples.

Example 1 A modified polyethylene was obtained by grafting 0.2% by weight of maleic anhydride onto LLDPE having an MI of 25 g / 10 minutes and a density of 0.916 g / cm ³ .

This was made into powder of 50 mesh passing with a crusher, and was lined to a thickness of 700 μ on an iron plate heated to 250 ° C. by a fluidized dipping method. Here, the tensile properties and the adhesive force of the coating film were tested by providing the iron plate with a portion to which the release agent was applied in advance and an uncoated portion.

After cooling, when the coating film on the part coated with the release agent was peeled off, it could be peeled off without breaking the film. Further, a tensile test was performed on both the peeled sheet and the pressed sheet according to JIS K6760. Table 1 shows the results.

On the other hand, when the adhesiveness with the iron plate was examined, it was found that the film had a sufficient adhesive force with the iron plate because the coating film broke without peeling.

The adhesion test is performed by making a 10 mm gap in the coating with a cutter knife, peeling the coating from one end, and then fixing the chuck to determine the strength when peeling at a speed of 50 mm / min in the 90 ° direction using a tensile tester. Recorded.

(Comparative Example 1) A modified polyethylene was obtained by grafting 0.2% by weight of maleic anhydride onto LLDPE having a MI of 20 g / 10 minutes and a density of 0.928 g / cm ^{3 in} the same manner as in Example 1.

This was made into a powder of 50 mesh passing with a pulverizer, and was lined to a thickness of 820 μ on an iron plate heated to 250 ° C. by a fluidized dipping method. The pretreatment method for the iron plate was the same as in Example 1.

After cooling, when the coating film was peeled off, the film was broken. Furthermore, a tensile test was performed on both the release film and the press sheet according to JIS K6760. Table 1 shows the results.

In addition, the adhesion was not accurately evaluated due to film breakage.

[Effects of the Invention] As described above, according to the powdered adhesive polyethylene for coating of the present invention, the linear low-density polyethylene whose melt index and density are specified is unsaturated fatty acid and / or
Alternatively, since it is modified with these acid anhydrides, it has excellent adhesiveness to metals and the like, and is extremely effective for coating, for example, by the fluid immersion method.

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Claims (1)

(57) [Claims] 1. A linear low density polyethylene having a melt index of 5 to 50 g / 10 minutes and a density of 0.910 to 0.925 g / cm ^3, which is modified with an unsaturated fatty acid and / or an acid anhydride thereof. Adhesive powder polyethylene for painting with a particle size of 30 mesh sieve.