JPS6132136B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a metal body coated with a polyethylene composition. More specifically, the present invention relates to a method for manufacturing a metal body coated with a polyethylene composition that has excellent cold resistance, heat resistance, adhesive strength, and cathodic peeling resistance. Polyethylene-coated metal bodies, especially polyethylene-coated steel pipes, have excellent cold resistance, corrosion resistance, water resistance, weather resistance, and impact resistance, so they are used as steel pipes for transporting gases or liquids such as gas, oil, and water, or for cable protection. Widely used as steel pipes. on the other hand,
Since polyethylene has poor adhesion to metals, there are methods of chemical conversion treatment of the metal surface, methods of blasting, methods of applying adhesives, methods of oxidizing polyethylene, and methods of copolymerizing polyethylene with acrylic acid, maleic anhydride, etc. Alternatively, a method of grafting and denaturation has been proposed. The present applicant previously proposed a method for improving the adhesive strength between metal and polyolefin by interposing an uncured epoxy resin adhesive between polyolefin modified with an unsaturated carboxylic acid or its anhydride and metal. Although a method (Japanese Patent Publication No. 53-4880) has been proposed, it was found to be insufficient for applications that require further adhesive strength. As a result of the studies conducted by the present inventors for this purpose, the metal body was coated with epoxy resin in advance, and after being heat-treated at a certain temperature or higher, a specific ethylene-α
- By heat-bonding polyethylene modified with unsaturated carboxylic acid or its anhydride to which an olefin random copolymer has been added, it has excellent adhesive strength not only at room temperature but also in cold and heat resistance. The present invention was achieved by finding that a metal body coated with a polyethylene composition having the following properties can be obtained. That is, the present invention applies 99 to 70% by weight of polyethylene (A) graft-modified with an unsaturated carboxylic acid or its anhydride after applying an epoxy resin adhesive to a metal body and heat-treating it at at least 50°C or higher.
and 1 to 30% by weight of an ethylene/α-olefin random copolymer (B) having an ethylene content of 30 to 95 mol% and a crystallinity of 0 to 20% by X-rays. The present invention provides a method for producing a metal body coated with a polyethylene composition, which is characterized in that the metal body is heat-bonded at a temperature higher than the melting point of the substance. The epoxy resin adhesive used to coat the metal body used in the method of the present invention is a polymolecular compound containing two or more highly reactive epoxy groups in the molecule, a Lewis base, an inorganic base, a primary amine, a It is a composition consisting of basic curing agents such as secondary amines and amides, acidic curing agents such as Lewis, phenol, carboxylic acids and carboxylic acid anhydrides, and various curing agents such as thiocol and alcohol. Diglycidyl ethers of various molecular weights consisting of bisphenol A and epichlorohydrin are usually used as multimolecular compounds containing two or more highly reactive epoxy groups in the molecule (hereinafter referred to as epoxy compounds), but other epoxy Compounds such as butyl glycidyl ether, 1,4-butanediol dicrycidyl ether, vinylcyclohexene dioxide, decyl glycidyl ether, dicycloaliphatic diether diepoxy, 2,2-bis[p-(2,3-epoxy) propoxy) phenyl]
-Propane, polyphenol formaldehyde poly(2,3-epoxypropyl) ether, poly-o-cresol formaldehyde poly(2,3)
-epoxypropyl)ether, 1,3-bis-
(2,3-epoxypropyl)benzene, 2,2
-Bis[4-(2,3-epoxypropoxy)-
3,5-dibromophenyl]propane, tetrakis(2,3-epoxypropoxy)diphenyl-
Methane, epoxidized polybutadiene, 2.4.
4'-tris(2,3-epoxypropoxy)-biphenyl, diglycidyl ether of linoleic acid dimer, bis(2,3-epoxycyclopentyl)
Ether, epoxy dicyclopentenyl phenyl glycidyl ether, triglycidyl-p-aminophenol, 3,4-epoxycyclohexylmethyl-(3,4-epoxy)cyclohexane carboxylate, epoxidized soybean oil, and others can also be used. . Further, specific examples of the curing agent include polymethylenediamine, diethylenetetramine, triethylenetetramine, aminoethylethanolamine, menthanediamine, N
- Aliphatic amines such as aminoethylpiperazine, 1,3-diaminocyclohexane, isophorone diamine, m-xylylene diamine and tetrachloro-p-xylylene diamine, m-phenylene diamine, 4,4'-methylene dianiline , diaminodiphenyl sulfone, aromatic amines such as benzidine and diaminodiphenyl ether, tetramethylguanidine, triethanolamine, N.
N'-dimethylpiperazine, N-methylmorpholine, pyridine, pyrazine, benzyldimethylamine, 2-(dimethylaminomethyl)phenol and 2,4,6-tris(dimethylaminomethyl)
Tertiary amines such as phenol, secondary amines such as piperidine and morpholine, 3,3'-dimethyl-
4,4'-diamino-dicyclohexylmethane,
3,9-bis(3-aminopropyl)-2,4.
Alicyclic polyamines such as 8,10-tetraoxospiro-[5,5]undecane and those modified with butyl glycidyl ether, Cardiura E, acrylonitrile, xylene diamine, etc.
Polyamide, urea, monomethylol urea, urea resin, melamine, hexamethoxymethylmelamine,
triallyl cyanurate, novolac, resol, phthalic acid, p-aminobenzoic acid, maleic acid, succinic anhydride, citraconic anhydride, itaconic anhydride, maleic anhydride, pyromellitic anhydride,
Examples include phthalic anhydride and trimellitic anhydride. Among these, aromatic amines, tertiary amines, secondary amines, alicyclic polyamines, and modified products thereof are preferred from the viewpoint of durability of adhesive strength. When applying the epoxy resin adhesive to the surface of a metal body, it may be applied by dissolving it in a solvent,
It may be applied directly or by melting. After applying the epoxy resin adhesive to the surface of the metal object, it is usually heated at a temperature of at least 50°C or higher, preferably 80 to 200°C, for 10 seconds or more before laminating the composition described below.
Must be heat treated for 60 minutes. Even if the composition described below is laminated without heat treatment, a coating having excellent heat resistance and adhesive strength cannot be obtained.
On the other hand, when the composition is laminated without applying an epoxy resin adhesive, although the initial adhesive strength is high, the resistance to cathodic peeling (when the metal is charged to become a cathode for cathodic protection) (resistance to peeling between layers) is poor. In the present invention, polyethylene (A) graft-modified with an unsaturated carboxylic acid or its anhydride refers to polyethylene grafted with an unsaturated carboxylic acid or its anhydride, or a blend of the grafted material and unmodified polyethylene. refers to something that has been done. Polyethylene as used herein refers to a homopolymer of ethylene or ethylene and other α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1- It is a copolymer mainly composed of ethylene with pentene, 1-decene, etc., and usually has a density of 0.910 to 0.970 g/cm ³ , a melt flow rate of 0.1 to 30 g/10 min, and a degree of crystallinity measured by X-rays of 45% or more. It is a crystalline thermoplastic resin polymerized by high-pressure method, medium/low pressure method, and is generally used as high-pressure polyethylene, low-pressure low-density polyethylene,
These are called medium density polyethylene and high density polyethylene. Examples of the unsaturated carboxylic acid or its anhydride to be grafted onto these polyethylenes include acrylic acid, methacrylic acid,
Examples include maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride, and among these, maleic anhydride is particularly preferred. Various known methods can be used to graft the unsaturated carboxylic acid or its anhydride onto polyethylene. For example, a method may be adopted in which both are heated to a high temperature in the presence or absence of a solvent, with or without the addition of a radical initiator. Other vinyl monomers such as styrene may be present in the graft reaction. The graft-modified polyethylene obtained in this way can be used as it is or after being blended with unmodified polyethylene to form the ethylene/α-olefin random copolymer described below.
Used in combination with (B). In either case, it is preferable that the amount of carboxylic acid or its anhydride in the composition is about 0.01 to 10% by weight as a unit. The ethylene/α-olefin random copolymer (B), which is another component of the composition used in the method of the present invention, has an ethylene content of 20 to 95 mol%, preferably 30 to 85 mol%, particularly preferably 35 to 75 mol% and X-ray crystallinity 0 to 20
%, preferably 0 to 10%. If the ethylene content exceeds 95 mol%, even when mixed with the above-mentioned graft-modified polyethylene (A), the effect of improving adhesive strength is small. Also, the ethylene content is 35
When the amount is between 75 mol % and 75 mol %, a coating having particularly excellent heat resistance and adhesive strength can be obtained.
On the other hand, if the ethylene content is less than 30 mol%, the compatibility with modified polyethylene is poor and the mechanical properties of the composition are impaired. If the X-ray crystallinity exceeds 20%, even if mixed with graft-modified polyethylene (A), the effect of improving adhesive strength and heat resistance will be small.
The α-olefin polymerized with ethylene is usually an α-olefin having 3 to 10 carbon atoms, and specifically, for example, propylene, 1-butene, 1-heptene, 1-hexene, 1-octene, 4-methyl-
Examples include 1-pentene and 1-decene. The ethylene/α-olefin random copolymer used in the method of the present invention is further copolymerized with a small amount of other monomers, such as dicyclopentadiene, ethylidenenorbornene, 1,4-hexadiene, etc., to the extent that the purpose of the present invention is not impaired. You can leave it alone. The ethylene/α-olefin random copolymer (B) used in the method of the present invention in the above range has good compatibility with the graft-modified polyethylene (A), so it is coated on a metal body as a composition with the graft-modified polyethylene (A). Even if you use it, it won't cause any bumps. On the other hand, even if polyisobutylene or the like is used in place of the ethylene/α-olefin random copolymer (B), it has poor compatibility with the graft-modified polyethylene (A) and may cause lumps when coated on a metal body. The composition used in the method of the present invention comprises the graft-modified polyethylene (A) and the ethylene/α-olefin random copolymer (B) in a ratio of (A)/(B)=99/1 to
70/30 (weight ratio), preferably 97/3 to 80/
It is a mixture in the range of 20. Ethylene α−
If the amount of the olefin random copolymer (B) is less than 1% by weight, the adhesive strength and its heat resistance will not be improved;
If it exceeds 30% by weight, heat-resistant adhesion will decrease.
and the mechanical properties of the composition are impaired. To obtain the composition, the graft-modified polyethylene (A) and the ethylene/α-olefin random copolymer (B) are mixed in the above range using various known methods such as a V-blender, a ribbon blender, a Henschel mixer, etc. , a method of mixing with a tumbler blender, etc., a method of granulating with an extruder, etc. after mixing, a method of melt kneading and mixing with an extruder, kneader, Banbury mixer, etc. can be adopted. In this case, at any stage of mixing, the composition may contain conventional polyolefins such as weathering stabilizers, heat stabilizers, antistatic agents, pigments, dyes, lubricants, nucleating agents, fillers, flame retardants, antiblocking agents, slip agents, etc. Various compounding agents used in addition to etc. may be blended within a range that does not impair the purpose of the present invention. The metal bodies used in the method of the present invention are plates, cylinders, tubes, or other shapes made of iron, copper, aluminum, nickel, cobalt, tin, zinc, or alloys containing these as main components. When applying the epoxy resin adhesive to the metal body, it is sufficient if the surface of the metal body is clean, but blasting or chemical conversion treatment is more effective. When coating the composition on a metal body that has been coated with an epoxy resin adhesive and heat-treated, it is necessary to carry out heat bonding at a temperature equal to or higher than the melting point of the composition. At that time, when coating a metal body with the composition in a molten state, it is not necessarily necessary to heat the metal body above the melting point of the composition, and even if the composition is coated on the metal body, it will immediately crystallize. The temperature may be maintained at a temperature that does not cause crystallization, for example, a temperature higher than the crystallization temperature. Various known methods can be used to coat the metal body with the composition, including electrostatic coating, fluidized dipping, fusing a film or sheet composition to the metal body, and extrusion coating. be able to. When coating a metal body with the composition, polyethylene may be coated on the outside of the composition so as to overlap the composition. In that case, the composition and polyethylene may be simultaneously coated in multiple layers using a coextrusion die, or the composition may be coated and then polyethylene may be coated. By the method described above, it is possible to obtain a polyethylene-coated metal body that has excellent cold resistance, heat resistance, adhesive strength, and cathode peeling resistance. It can be widely used for etc. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. Example 1 After sandblasting a steel plate (SS41) of 50 x 150 x 1.6 mm (thickness), an epoxy resin adhesive with the trade name Epicoat 828 (Ciel Chemical: bisphenol A epoxy resin molecular weight approximately 380) was used. A mixture of Epomate B-002 (Mitsubishi Yuka: heterocyclic amine curing agent) at a ratio of 2:1 (weight ratio) was applied and heat treated at 200°C for 5 minutes. Then apply a melt flow rate of 13g/
10min (ASTM D1238:E) and density 0.965g/ ^cm3
Polyethylene grafted with maleic anhydride (maleic anhydride content 1.6wt%: hereinafter referred to as PE-M
) 5% by weight, ethylene content 80 mol%,
Linear crystallinity 0.2%, density 0.86g/ ^cm3 and melt flow rate 0.4g/10min (ASTM D1238:
L) ethylene-propylene random copolymer (hereinafter abbreviated as EPR-I): 10% by weight and ethylene content 98 mol%, density 0.935g/cm ³ and melt flow rate 1.4g/10min (ASTM D1238:E) 85% by weight of ethylene/1-butene copolymer (hereinafter abbreviated as MDPE) was mixed in a Henschel mixer and granulated in a single screw extruder.The composition was then molded in a sheet molding machine to form a 0.25 mm thick sheet and high density. A polyethylene-coated metal plate was obtained by stacking 3 mm thick sheets of polyethylene (trade name Hi-Zex 5100E manufactured by Mitsui Petrochemical Industries KK; hereinafter abbreviated as HDPE) and adhering them at a temperature of 150°C for 10 minutes at a pressure of 50 kg/cm ² . Ta. Next, the performance of the coated metal plate was measured by the following method. Peeling test: Using an Instron tensile tester (manufactured by Instron, USA) at a peeling rate of 50 mm/min.
Peel strength (Kg/cm) was measured by the 90 degree peel method (test piece width: 10 mm, measurement temperature -40°C, 23°C and 80°C) Cathode peel test: According to ASTM G8, the hole in the test piece was 5mmφ, 1 at 20°C in a saline electrolyte with a concentration of 3%.
A one-month test and a two-month test were conducted to determine the peeling distance (mm) of the polyethylene coating layer from the hole in the test piece. Examples 2 and 3 In place of the composition used in Example 1, PE-
M:ERR-I:MDPE=5:15:80 and 5:
The same procedure as in Example 1 was carried out except that a composition consisting of 20:75 (wt%) was used. The results are shown in Table 1. Examples 4 to 6 Instead of EPR-I used in Example 1, ethylene content was 80 mol%, X-ray crystallinity was 0.2%,
Density 0.86g/cm ³ and melt flow rate 0.2g/
Ethylene-propylene random copolymer (hereinafter abbreviated as EPR-) for 10min (ASTM D1238: L)
PE-M and
Example 1 except using a composition mixed with MDPE
I went in the same way. The results are shown in Table 1. Examples 7 to 9 Instead of EPR-I used in Examples 4 to 6, ethylene content was 40 mol%, crystallinity by X-ray was 1
%, density 0.87g/ ^cm3 and melt flow rate 0.2
The same procedure as in Examples 4 to 6 was carried out except for using an ethylene-propylene random copolymer (hereinafter abbreviated as EPR-) of g/10 min. The results are shown in Table 1. Example 10 Instead of EPR-I used in Example 1, ethylene content was 72 mol%, X-ray crystallinity was 2%, density was 0.87 g/cm ³ , iodine number was 16, and Mooney viscosity was used.
80ML ₁₊₄ Ethylene-propylene-ethylidenenorbornene terpolymer (hereinafter referred to as EPT-I) at 100℃
Example 1 was carried out in the same manner as in Example 1, except for using . The results are shown in Table 1. Examples 11 and 12 The heat treatment conditions for the epoxy resin adhesive in Example 2 were 120° C. for 5 minutes and 150° C. for 5 minutes, respectively. The results are shown in Table 1. Examples 13 and 14 The same procedure as in Example 8 was conducted except that the heat treatment conditions for the epoxy resin adhesive in Example 8 were 120° C. for 5 minutes and 150° C. for 5 minutes, respectively. The results are shown in Table 1. Comparative Examples 1-3 PE-M instead of the composition used in Example 1:
A composition of MDPE=5:95 (wt%) was used, and the heat treatment conditions of the epoxy resin adhesive were adjusted respectively.
The same procedure as in Example 1 was conducted except that the heating times were 120°C for 5 minutes, 150°C for 5 minutes, and 200°C for 5 minutes. The results are shown in Table 1. Comparative Examples 4 and 5 A steel plate that was simply sandblasted without applying the epoxy resin adhesive used in Example 1 was
℃ x 5 minutes, each PE-M as a composition:
EPR-I: MDPE and PE-M: EPR-:
The same procedure as in Example 1 was carried out except that a composition consisting of MDPE=5:15:80 (wt%) was used. The results are shown in Table 1. Comparative Example 6 Polyisobutylene (trade name Vistanex MML-80) was used instead of EPR-I used in Example 1.
The same procedure as in Example 1 was conducted except that a pulverized product (hereinafter abbreviated as PIB) was used. As a result, when the sheet was formed, bumps appeared and a good sheet could not be obtained.

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Claims (1)

[Claims] 1 After applying an epoxy resin adhesive to a metal body and heat-treating it at a temperature of at least 50°C or higher, 99 to 70% by weight of polyethylene (A) graft-modified with an unsaturated carboxylic acid or its anhydride and an ethylene content
A polyethylene composition consisting of 30 to 95 mol% and 1 to 30% by weight of an ethylene/α-olefin random copolymer (B) having a crystallinity of 0 to 20% by A method for producing a metal body coated with a polyethylene composition, characterized by heat bonding at a temperature.