JPH0128770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene sheet for lamination that has good adhesion to metals and high temperature heat resistance.

Since polypropylene is nonpolar, it exhibits almost no adhesion to metals. Conventionally, in order to improve adhesion, methods of applying surface treatments such as corona discharge treatment, chromic acid treatment, flame treatment, and etching to the surface of polypropylene or (and) metal, and modified polyolefins in which maleic anhydride is grafted to polyolefins have been used. (e.g., Japanese Patent Publication No. 10757/1982, Japanese Patent Publication No. 47-4822), a method using a composition in which acid-modified polyolefin is blended with a synthetic hydrocarbon elastomer or an ethylene polymer (e.g., Japanese Patent Publication No. 80334/1989, 56-21850) are known. However, when the modified polypropylene produced by these methods is laminated with metal, it easily deforms due to its own weight or external force when the temperature exceeds the melting point of the polypropylene.
There is a problem with high temperature resistance.

Generally, it is well known that crosslinking of polymeric substances greatly improves their melt resistance to alteration and improves their high-temperature heat resistance. However, polypropylene is a thermally decomposable polymer, and when mixed with an organic peroxide and heated, crosslinking does not occur, but on the contrary, it decomposes and its viscosity decreases. Therefore, in order to thermally crosslink polypropylene, a method has been adopted in which a crosslinking aid such as divinylbenzene or liquid 1,2 polybutadiene is mixed with a radical generator and heated. However, the crosslinked polypropylene thus obtained not only does not adhere to metal at all, but it is extremely difficult to form it into, for example, a film or sheet.

As a result of extensive research into polypropylene, which has good adhesion to metals and excellent high-temperature heat resistance, the present inventors discovered that a specific The present invention was proposed based on the discovery that a desired laminate with metal or the like can be obtained by using a sheet formed at a temperature of . That is, the present invention comprises polypropylene with a melting point of 130 to 170°C, unsaturated carboxylic acids having one double bond, a crosslinking aid, and an organic peroxide whose 1-minute half-life temperature is 10°C or more higher than the melting point of the polypropylene. This polypropylene sheet for lamination is formed from a composition at a temperature higher than the melting point of the polypropylene and lower than the 1-minute half-life temperature of the organic peroxide. Note that the term "sheet" used in the present invention is suitable for forming adhesive layers and laminates with metals, etc., and includes general sheet-like materials and film-like materials.

The polypropylene used in the present invention is not particularly limited, and includes homopolypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, propylene and α-
Copolymers with olefins, mixtures thereof, and the like are used. Among these, especially propylene-ethylene random copolymer and propylene-ethylene
Ethylene block copolymers are preferably used. The melting point of these polypropylenes varies depending on the tacticity and comonomer content, but is generally in the range of 130 to 170°C.

Furthermore, the unsaturated carboxylic acids used in the present invention are not particularly limited as long as they have one reactive double bond, and representative examples of the unsaturated carboxylic acids include: , such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid,
Also, these acid anhydrides, esters, amides, imides, metal salts, etc., such as maleic anhydride, citraconic anhydride, itaconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, Butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, monoethyl maleate,
Maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-
N,N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide,
Fumaric acid-N-monoethylamide, fumaric acid-
N,N-diethylamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, Examples include potassium methacrylate. Among these, maleic anhydride and metal salts of unsaturated carboxylic acids are preferably used. The amount of such unsaturated carboxylic acids used is not particularly limited, but in order to obtain a laminate with good adhesiveness, it is generally 0.01 to 20 parts by weight per 100 parts by weight of polypropylene.
Preferably, it is necessary to add 0.1 to 10 parts by weight.

The crosslinking auxiliary agent used in the present invention is a compound having two or more double bonds in one molecule, such as a compound with a number average molecular weight of 500 and mainly composed of divinylbenzene, diallyl phthalate, triallyl glycerate, and diene monomer. ~10000 liquid rubber, e.g. 1,
2-polybutadiene, 1,4-polybutadiene,
Styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, or 1,2-polybutadiene having functional groups such as carboxyl group, hydroxyl group, mercapto group, halogen atom, amino group, aziridino group, and epoxy group in the molecule,
Examples include 1,4-polybutadiene, polyisoprene, polychloroprene, 1,2-polypentadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, butadiene-isoprene copolymer, butadiene-pentadiene copolymer, and divinylbenzene and liquid 1,2 -Polybutadiene is preferably used. The amount of crosslinking aid added is based on modified polypropylene.
The amount is 1 to 50 parts by weight per 100 parts by weight, preferably 3 to 30 parts by weight per 100 parts by weight of polypropylene. If the amount of the crosslinking aid added is less than 1 part by weight, the effect of improving high temperature heat resistance will be small, and if it exceeds 50 parts by weight, the rigidity will drop below the melting point of polypropylene, which is undesirable.

In the present invention, as an organic peroxide, the 1-minute half-life temperature (temperature at which it decomposes by half in 1 minute) is lower than the melting point of polypropylene (the peak temperature of the endothermic curve measured at a heating rate of 10°C/min with a differential scanning calorimeter). 10℃
It is important to use one that is higher than that. As mentioned above, the melting point of polypropylene is generally 130 to 170°C.
Since the temperature is within the temperature range of
Organic peroxides with temperatures above 140°C are used. Examples of such organic peroxides include 2,4,4-trimethylpentyl-2-hydroperoxide,
Diisopropylbenzene hydroperoxide, cumain hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexane, 1,3- Bis-(t
-butylperoxy-isopropyl)-benzene,
t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-
di-(t-butylperoxy)-hexyne-3,
1,1-di-t-butylperoxy-3,3,5
-trimethylcyclohexane, 1,1-di-t-
Butylperoxycyclohexane, 2,2-di-
(t-butylperoxy)-butane, 4,4-di-
t-Butyl peroxyvaleric acid-n-
Butyl ester, di-t-butylperoxy-hexahydroterephthalate, di-t-butylperoxyazelate, t-butylperoxy-
3,5,5-tolumethylhexoate, t-butylperoxyacetate, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, succinic acid peroxide, vinyl tris-(t-butylperoxy)
Silane, etc. The amount of organic peroxide added varies depending on the amount of crosslinking aid added, but is generally preferably 0.1 to 10 parts by weight per 100 parts by weight of polypropylene. If the amount of organic peroxide added is less than 0.1 parts by weight, the degree of crosslinking will be low, and if it exceeds 10 parts by weight, decomposition will occur and the effect of improving high temperature heat resistance will be small, which is not preferable.

The present invention includes polypropylene with a melting point of 130 to 170°C, unsaturated carboxylic acids having one double bond, crosslinking aids, organic peroxides, other polymeric substances other than polypropylene, fillers, etc. as necessary. Additives are mixed to obtain a polypropylene composition. Mixing is carried out using a tumbler blender, a V-type blender, a Henschel mixer, a ribbon mixer, or the like. In some cases, these mixtures may be melt-kneaded using a screw extruder, mixing roll, Banbury mixer, etc. at a temperature higher than the melting point of polypropylene and lower than the one-minute half-life temperature of the organic peroxide. Next, the present invention provides that one of the organic peroxides contained in the polypropylene composition at a temperature higher than the melting point of the polypropylene is
Obtain the desired sheet at a temperature lower than the half-life temperature for minutes.

The thus obtained polypropylene sheet of the present invention can be pressure-bonded to a metal or the like at a temperature equal to or higher than the 1-minute half-life temperature of the organic peroxide contained in the sheet to obtain a laminate with good adhesion and excellent high-temperature heat resistance. I can do it. There are no particular restrictions on the metals used for lamination; iron, aluminum, chromium, nickel, gold, silver, copper, magnesium, zinc, tin,
Examples include lead, steel, stainless steel, galvanized iron, and tinplate, with iron and aluminum being preferably used.

The polypropylene/metal laminate obtained in the above manner has strong adhesive strength between the two, excellent high-temperature heat resistance, and has both the excellent characteristics of polypropylene and the excellent characteristics of metal. It also has excellent new features that other manufacturers do not have, making it suitable for automobile materials, industrial materials,
It can be effectively used as building materials, beverage cans, packaging materials for various foods, etc.

Examples of the laminate of the present invention are shown below, but the present invention is not limited thereto.

The adhesive strength and high temperature heat resistance of the laminates in Examples were measured by the following methods.

Adhesive strength is measured between two 2cm wide metal sheets.
It is expressed as T-peel strength of a three-layer laminate with a layer of modified polypropylene composition 0.1 mm thick. The measurement is
The test was carried out at 23°C and 50% RH at a tensile speed of 20 mm/min.

The measurement of high temperature heat resistance is carried out between two parallel metal sheets facing each other so that the overlap length is 2 cm.
A three-layer laminate with a modified polypropylene composition layer of 0.1 mm thickness was placed in an oven at 200°C, one metal sheet was suspended by a wire, and after 10 minutes, a load of 200 g was applied to the lower metal sheet, and both metal sheets were suspended. The time required for the sheets to separate is expressed. The thickness of the metal sheets is 0.2 mm for the iron sheet and 0.1 mm for the aluminum sheet, and these are sufficiently degreased.

The polypropylene/metal laminate with one or more layers obtained as described above has strong adhesive strength between the two, excellent high-temperature heat resistance, and has both the excellent characteristics of polypropylene and the excellent characteristics of metal. Furthermore, it has excellent new features such as not having polypropylene or metal, so it can be effectively used as automobile materials, industrial materials, building materials, beverage cans, packaging materials for various foods, etc.

Examples of the present invention will be given below, and the mode of use as a laminate will be shown, but the present invention is not limited thereto.

The adhesive strength and high temperature heat resistance of the laminates obtained in Examples were measured by the following methods.

Adhesive strength is measured between two 2cm wide metal sheets.
3 with 0.1mm thick polypropylene composition layer
It is expressed as the T-peel strength of the layer laminate. The measurement is 23
The test was carried out at a tensile strength of 20 mm/min at 50% RH.

The measurement of high temperature heat resistance was carried out by placing a 0.1
A three-layer laminate with a polypropylene composition layer of mm thickness was placed in an oven at 200°C, one metal sheet was suspended by a wire, and after 10 minutes, a load of 200 g was applied to the lower metal sheet, and both metal sheets were It is expressed as the time until separation. The thickness of the metal sheets is 0.2 mm for the iron sheet and 0.1 mm for the aluminum sheet, and these are sufficiently degreased.

Example 1 MFI=0.6g/10min, propylene-ethylene random copolymer with ethylene content of 3.0% (melting point 140°C)
100 parts by weight, 5 parts by weight of calcium methacrylate,
10 parts by weight of divinylbenzene, 2.0 parts by weight of dicumyl peroxide (1 minute half-life temperature 179°C), 0.1 part by weight of butylated hydroxytoluene, and 0.1 part by weight of calcium stearate were mixed in a Henschel mixer for 5 parts by weight.
The mixture was mixed for a minute, and a laminated sheet of the present invention having a thickness of 0.1 mm was formed at 165° C. using an extruder equipped with a T-die. This sheet was sandwiched between 2 cm wide aluminum sheets and pressed together at a temperature of 170° C. and a pressure of 10 kg/cm ² for 5 minutes, and then heated at 220° C. for 5 minutes. The adhesive strength of the laminate thus obtained was 15.3Kg/
2 cm, high temperature heat resistance was 1 hour or more.

Comparative Example 1 The same procedure as in Example 1 was carried out except that benzoyl peroxide (1 minute half-life temperature: 130° C.) was used instead of dicumyl peroxide. In the case of sheet molding, the extrudate became flaky and no sheet could be obtained.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the sheet extrusion temperature was changed to 220°C. The extrudate became flaky and no sheet could be obtained.

Comparative Example 3 The same procedure as in Example 1 was carried out except that calcium methacrylate was not added. The adhesive strength of the obtained laminate was 0.

Comparative Example 4 The same procedure as in Example 1 was carried out except that divinylbenzene was not added. The adhesive strength of the obtained laminate was 1.1Kg/2cm, and the high temperature resistance was 10.
It was less than a second.

Comparative Example 5 The same procedure as in Example 1 was carried out except that dicumyl peroxide was not added. The resulting laminate had an adhesive strength of 0.4 kg/2 cm and a high temperature resistance of 50 seconds.

Example 2 Propylene-ethylene block copolymer with MFI = 1.5 g/10 min and ethylene content of 2.7% by weight (melting point
160℃) 100 parts by weight, 40 parts by weight of calcium carbonate with an average particle size of 1.2μ, 0.5 parts by weight of maleic anhydride, 20 parts by weight of liquid 1,2-polybutadiene with a number average molecular weight of 1000, 2,5-dimethyl-2,5 -di-(t-butylperoxy)-hexyne-3 (1 minute half temperature
193℃) 3 parts by weight, butylated hydroxytoluene
0.1 part by weight and 0.1 part by weight of calcium stearate were mixed for 5 minutes using a Henschel mixer, and melt-kneaded and pelletized using a CCM extruder at 170°C.
From the obtained polypropylene composition pellets, T-
A laminating sheet of the present invention having a thickness of 0.1 mm was formed at 175° C. using an extruder equipped with a die. This sheet was sandwiched between 2 cm wide iron sheets and pressed together at a temperature of 220° C. and a pressure of 10 kg/cm ² for 10 minutes. The adhesive strength of the thus obtained laminate was 10.8 kg/2 cm, and the high temperature heat resistance was over 1 hour.

Comparative Example 6 In Example 2, 2,5-dimethyl-2,5
The procedure of Example 2 was repeated except that benzoyl peroxide was used in place of -di-(t-butylperoxy)-hexyne-3.

When pelletizing using a CCM extruder, the extrudate became flaky and clean pellets could not be obtained.

Comparative Example 7 The same procedure as in Example 2 was carried out except that the sheet extrusion temperature was changed to 220°C. The extrudate became flaky and no sheet could be obtained.

Comparative Example 8 The same procedure as in Example 2 was carried out except that maleic anhydride was not added. The adhesive strength of the obtained laminate was 0.

Comparative Example 9 The same procedure as in Example 2 was conducted except that liquid 1,2-polybutadiene was not added.
The adhesive strength of the obtained laminate was 5.5 kg/2 cm, and the high temperature heat resistance was 10 seconds or less.

Comparative Example 10 In Example 2, 2,5-dimethyl-2,5
The procedure of Example 2 was repeated except that -di-(t-butylperoxy)-hexyne-3 was not added. The adhesive strength of the obtained laminate was 0.2Kg/2cm.
High temperature heat resistance was 260 seconds.

Comparative Example 11 The same procedure as in Example 2 was carried out except that ethylene glycol diacrylate was used in place of maleic anhydride. The adhesive strength of the obtained laminate is
0.2Kg/2cm, high temperature heat resistance was over 1 hour.

Claims (1)

[Claims] 1. From polypropylene with a melting point of 130 to 170°C, unsaturated carboxylic acids having one double bond, a crosslinking aid, and an organic peroxide whose 1-minute half-life temperature is 10°C or more higher than the melting point of the polypropylene. A polypropylene sheet for lamination, which is formed from a composition comprising: at a temperature higher than the melting point of the polypropylene and lower than the 1-minute half-life temperature of the organic peroxide. 2. The sheet according to claim 1, wherein the unsaturated carboxylic acid is maleic anhydride. 3. The sheet according to claim 1, wherein the unsaturated carboxylic acid is an unsaturated carboxylic acid metal salt. 4. The sheet according to claim 1, wherein the crosslinking aid is liquid 1,2-polybutadiene or dinylbenzene. 5. The sheet according to claim 1, wherein the organic peroxide is dicumyl peroxide or 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3.