JPS6247450B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene sheet for lamination having good adhesion to metals and high temperature heat resistance, and a method for producing the same.

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, and there is a problem that it has poor high-temperature heat resistance.

In general, 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 a radical generator is mixed with it 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 that has good adhesion to metals and excellent high-temperature heat resistance, the present inventors have obtained a desired polypropylene sheet for lamination by crosslinking modified polypropylene, and have provided the present invention. This is what I came to do. That is,
According to the present invention, a polypropylene sheet for lamination is provided in which part or all of polypropylene is grafted with an unsaturated carboxylic acid and crosslinked to have a gel fraction in the range of 10 to 90%. Although the method for producing the polypropylene sheet for lamination of the present invention is not particularly limited, the following method is particularly recommended. That is, modified polypropylene in which part or all of the polypropylene is grafted with unsaturated carboxylic acids,
A composition comprising a crosslinking aid and a radical generator having a one-minute half-life temperature higher than the melting point of the modified polypropylene is formed into a sheet at a temperature higher than the melting point of the modified polypropylene and lower than the one-minute half-life temperature of the radical generator. There is also provided a method for producing a polypropylene sheet for lamination, which comprises subsequently heating the radical generator to a temperature equal to or higher than the one-minute half-life temperature of the radical generator. In addition, a composition comprising polypropylene, unsaturated carboxylic acids, a crosslinking aid, and a radical generator having a 1-minute half-life temperature higher than the melting point of the polypropylene is heated at a temperature higher than the 1-minute half-life temperature of the radical generator at a temperature higher than the melting point of the polypropylene. This is a polypropylene sheet for lamination, which is formed into a sheet at a low temperature and then heated to a temperature equal to or higher than the 1-minute half-life temperature of the radical generator.

The modified polypropylene used in the present invention can be obtained by grafting unsaturated carboxylic acids onto polypropylene by any method.
The graft content of unsaturated carboxylic acids in the modified polypropylene is generally preferably from 0.005 to 5% by weight. The method for producing such modified polypropylene is not particularly limited, and includes, for example, a method of reacting in a molten state (e.g., Japanese Patent Publication No. 43-27421), a method of reacting in a solution state (e.g., Japanese Patent Publication No. 44-15422),
A method of reacting in a slurry state (for example,
-18144), a method of reacting in a gas phase (for example, JP-A-50-77493), and the like.

The polypropylene used in the present invention is not particularly limited, and includes homopolypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, copolymer of propylene and α-olefin, and mixtures thereof. used. Among these, propylene-ethylene random copolymers and propylene-ethylene block copolymers are particularly preferably used. The melting point of these polypropylenes varies depending on the tacticity and comonomer content, but is generally between 130 and 170.
in the range of ℃.

Examples of unsaturated carboxylic acids used in the present invention include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and their acid anhydrides, esters, amides, imides, metal salts, etc. For example, maleic anhydride, citraconic anhydride, itaconic anhydride, methyl acrylate,
Ethyl methacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl itaconate, diethyl itaconate , 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-
Examples include phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, and the like. Among these, it is most preferable to use maleic anhydride.

The crosslinking auxiliary agent used in the specified production method of the present invention is a compound having two or more double bonds in one molecule, and includes, for example, divinylbenzene, diallylphthalate, triallylglycerate, and diene monomer as main components. Number average molecular weight: 500~
10,000 liquid rubbers, such as 1,2-polybutadiene, 1,4-polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, or carboxyl groups in the molecule,
1,2-polybutadiene, 1,4-polybutadiene, polyisoprene, polychloroprene, having functional groups such as hydroxyl group, mercapto group, halogen atom, amino group, aziridino group, epoxy group, etc.
1,2-polypentadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, butadiene-isoprene copolymer,
Examples include butadiene-pentadiene copolymers, and divinylbenzene and liquid 1,2-polybutadiene are preferably used. The amount of crosslinking aid added is modified polypropylene or 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 modified polypropylene or 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, not only will the adhesiveness of the modified polypropylene composition sheet obtained decrease, but also the A significant decrease in rigidity is undesirable.

Next, the radical generator used in the present invention has a one-minute half-life temperature (temperature at which it decomposes by half in one minute).
is higher than the melting point of modified polypropylene or polypropylene (the peak temperature of an endothermic curve measured with a differential scanning calorimeter at a heating rate of 10°C/min), preferably 10°C or more higher. The melting point of modified polypropylene or polypropylene is in the temperature range of 130 to 170℃, so the 1 minute half-life temperature is 130℃ or higher,
Preferably, a radical generator having a temperature of 140°C or higher can be used. Examples of radical generators used in the present invention include 2,4,4-trimethylpentyl-2-hydroperoxide, diisopropylbenzene hydroperoxide, cumene 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 -Butylperoxyvaleric acid-n-butyl ester, di-t-butylperoxy-hexahydroterephthalate, di-t-butylperoxyazelate, t-butylperoxy-3,5,5-trimethyl xolate, t-butyl peroxyacetate, t-butyl peroxybenzoate,
t-Butylperoxyisopropyl carbonate
succinic acid peroxide, vinyltris-(t-butylperoxy)silane, and the like. The amount of radical generator added varies depending on the amount of crosslinking aid added, but generally it is 0.1 parts by weight per 100 parts by weight of modified polypropylene or polypropylene.
~10 parts by weight is preferred. If the amount of radical generator added is less than 0.1 part by weight, the degree of crosslinking will be low;
If it exceeds 1 part by weight, decomposition will occur and the effect of improving high temperature heat resistance will be small, which is not preferable.

In the production method of the present invention, modified polypropylene, a crosslinking aid, a radical generator, other unmodified polypropylene, other polymeric substances other than polypropylene, inorganic or organic fillers, heat-resistant stabilizers, weather-resistant stabilizers, etc. agents, lubricants, nucleating agents, pigments, dyes,
Additives such as flame retardants and anti-blocking agents are mixed. In another embodiment, polypropylene, unsaturated carboxylic acids, crosslinking aids, radical generators, and in some cases other polymeric substances other than polypropylene, fillers, and other additives are mixed. Mixing is carried out using a tumbler blender, a V-type blender, a Henschel mixer, a ribbon mixer, or the like. In some cases, the mixture may be melt-kneaded using a screw extruder, mixing roll, Banbury mixer, etc. at a temperature higher than the melting point of the modified polypropylene or polypropylene and lower than the one-minute half-life temperature of the radical generator.

Next, the composition thus obtained is formed into a film or sheet (hereinafter collectively referred to as a sheet) at a temperature lower than the one-minute half-life temperature of the radical generator. The molding method is not particularly limited, for example, an extruder with a T-die, a calendar molding machine,
This can be done using a compression molding machine or the like.

Next, the sheet-like material obtained as described above is heated to a temperature equal to or higher than the 1-minute half-life temperature of the radical generator. The heating method is not particularly limited, and examples thereof include air bath heating, liquid bath heating, solid contact heating, infrared heating, and high frequency heating. The heating time varies depending on the decomposition temperature of the radical generator, but generally 10 seconds to 1 hour is appropriate.

In addition to the method using the radical generator, the method for obtaining the crosslinked polypropylene sheet in the present invention is to form a modified polypropylene or a composition consisting of polypropylene and a crosslinking aid into a sheet and then use radiation. A method of crosslinking may also be adopted.

The degree of crosslinking of the polypropylene sheet in the present invention is 10 to 90% in terms of gel fraction, preferably 30 to 80%.
%. If the degree of crosslinking is too high, adhesion will be poor in lamination, which is not preferred.

By pressing the polypropylene sheet obtained by the above method with a metal or the like at a temperature higher than the melting point of the sheet, a laminate having good adhesion and excellent high temperature heat resistance can be obtained. There are no particular restrictions on the metals used for lamination, and examples include iron, aluminum, chromium, nickel, gold, silver, copper, magnesium, zinc, tin, lead, steel, stainless steel, galvanized iron, and tinplate. Aluminum is 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 was carried out by placing a 0.1
The layer laminate with a polypropylene composition layer of mm thickness is placed in an oven at 200 °C, one metal sheet is suspended by a wire, and after 10 minutes the lower metal sheet is attached.
It is expressed as the time until the two metal sheets separate under a load of 200g. The thickness of the metal sheet is
The iron sheet is 0.2mm thick and the aluminum sheet is 0.1mm thick, and these have been thoroughly degreased.

Example 1 MFI = 0.6 g/10 min, 100 parts by weight of propylene-ethylene random copolymer with ethylene content of 2.0% by weight, 2 parts by weight of maleic anhydride, 2,5-dimethyl-2,5-di(t-butyl) (peroxy)-hexane 0.12 parts by weight, butylated hydroxytoluene 0.1
parts by weight and 0.1 parts by weight of calcium stearate were mixed in a Henschel mixer for 5 minutes, and L/D = 24.
The mixture was melt-kneaded and pelletized using a 40 mmφ extruder at 220°C, followed by heat treatment at 145°C for 4 hours using a constant temperature dryer to obtain modified polypropylene.
This modified polypropylene contained 0.5% by weight of maleic anhydride grafted therein.

15 parts by weight of this modified polypropylene, MFI=4.0
g/10 min, unmodified propylene-ethylene random copolymer with ethylene content of 3.0% by weight (melting point 140
°C) 85 parts by weight, divinylbenzene 10 parts by weight, dicumyl peroxide (1 minute half-life temperature 179 °C) 2.0
parts by weight, 0.1 parts by weight of butylated hydroxytoluene, and 0.1 parts by weight of calcium stearate, mixed for 5 minutes in a Henschel mixer,
A sheet with a thickness of 0.1 mm was formed at 165° C. using an extruder equipped with a T-die. Subsequently, this sheet was heated at 250° C. for 5 minutes using an infrared heater. The degree of crosslinking of the obtained sheet was 84% in terms of gel fraction. The sheet obtained in this way was sandwiched between 2 cm wide aluminum sheets, and the temperature was 240°C.
Compression heating was performed for 5 minutes at a pressure of cm ² . The adhesive strength of the obtained laminate was 2.3 kg/2 cm, and the high temperature heat resistance was over 1 hour.

Comparative Example 1 The same procedure as in Example 1 was conducted except that benzoyl peroxide (1 minute half-life temperature: 130° C.) was used instead of dicumyl peroxide. When extruding sheets, the extrudates were flaky and no sheets were 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 was obtained.

Comparative Example 3 The same procedure as in Example 1 was carried out except that the modified polypropylene was not added and the unmodified propylene-ethylene random copolymer was used in an amount of 100 parts by weight. The adhesive strength of the obtained laminate was 0.

Comparative Example 4 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 0.6 kg/2 cm and a high temperature resistance of 70 seconds.

Comparative Example 5 The same procedure as in Example 1 was carried out except that divinylbenzene and dicumyl peroxide were not added. The resulting laminate had an adhesive strength of 1.9 kg/2 cm and a high temperature resistance of 80 seconds.

Example 2 15 parts by weight of modified polypropylene obtained in Example 1, MFI = 1.5 g/10 min, 85 parts by weight of unmodified propylene-ethylene block copolymer with ethylene content of 2.7% by weight (melting point 160°C), average particle size 40 parts by weight of calcium carbonate having a molecular weight of 1.2μ, 20 parts by weight of liquid modified 1,2-polybutadiene having a number average molecular weight of 1000, 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3(1 half-life temperature 193℃) 3 parts by weight,
A composition consisting of 0.1 part by weight of butylated bidroxytoluene and 0.1 part by weight of calcium stearate was mixed for 5 minutes using a Henschel mixer, and then melt-kneaded and pelletized using a CCM extruder at 170°C.
A sheet having a thickness of 0.1 mm was formed from the obtained modified polypropylene composition pellets at 175 DEG C. using an extruder equipped with a T-die. The obtained sheet was heated at 250° C. for 10 minutes using an infrared heater. The degree of crosslinking of the obtained sheet was 70% in terms of gel fraction. This sheet was sandwiched between 2 cm wide iron sheets, and the temperature was 240℃.
Pressing was carried out for 10 minutes at a pressure of 10 kg/cm ² . The adhesive strength of the thus obtained laminate was 12.7 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 instead of -di-(t-butylperoxy)-hexyne-3. During pelletization using a CCM extruder, the extrudate became flaky and good pellets could not be obtained.

Comparative Example 7 The same procedure as in Example 2 was carried out except that the modified polypropylene was not added and the unmodified propylene-ethylene block copolymer was used in an amount of 100 parts by weight. The adhesive strength of the obtained laminate was 0.

Comparative Example 8 In Example 2, 2,5-dimethyl-2,5-
The same procedure as in Example 2 was carried out except that di-(t-butylperoxy)-hexyne-3 was not added.
The resulting laminate had an adhesive strength of 0.5 kg/2 cm and a high temperature resistance of 60 seconds.

Comparative Example 9 Same as Example 2 except that liquid 1,2-polybutadiene and 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3 were not added in Example 2. I went to The adhesive strength of the obtained laminate was 10.2Kg/2cm, and the high temperature resistance was
It was hot in 110 seconds.

Example 3 Propylene-ethylene random copolymer with MFI = 0.6 g/10 min and ethylene content of 3.0% (melting point 140
℃) 100 parts by weight, calcium methacrylate 5 parts by weight, divinylbenzene 10 parts by weight, dicumyl peroxide (1 minute half-life temperature 179°C) 2.0 parts by weight,
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 minutes, and then mixed with an extruder with a T-die for 165
A sheet with a thickness of 0.1 mm was formed at ℃. Subsequently, it was heated at 250°C for 20 minutes using an infrared heater. The degree of crosslinking of the obtained sheet was 83% in terms of gel fraction. This sheet was sandwiched between 2 cm wide aluminum sheets and pressed together at a temperature of 220° C. and a pressure of 10 kg/cm ² for 5 minutes. The thus obtained laminate had an adhesive strength of 4.5 kg/2 cm and a high temperature heat resistance of 1 hour or more.

Comparative Example 10 Example 3 was carried out in the same manner as in Example 3, 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 11 The same procedure as in Example 3 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 12 The same procedure as in Example 3 was carried out except that calcium methacrylate was not added. The adhesive strength of the obtained laminate was 0.

Comparative Example 13 The same procedure as in Example 3 was conducted except that divinylbenzene was not added and the amount of dicumyl peroxide added was 0.1 parts by weight. The adhesive strength of the obtained laminate was 1.5 kg/2 cm, and the high temperature heat resistance was 10 seconds or less.

Comparative Example 14 The same procedure as in Example 3 was carried out except that dicumyl peroxide was not added. The resulting laminate had an adhesive strength of 0.2 kg/2 cm and a high temperature resistance of 60 seconds.

Example 4 Propylene-ethylene block copolymer (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 3 parts by weight of -di-(t-butylperoxy)-hexyne-3 (1 minute half-life temperature 193°C), 0.1 part by weight of butylated bidroxytoluene, and 0.1 part by weight of calcium stearate were mixed in a Henschel mixer for 5 minutes, Melt-kneading pelletization was performed at 170°C using a CCM extruder. A sheet having a thickness of 0.1 mm was formed from the obtained polypropylene composition pellets at 175 DEG C. using an extruder equipped with a T-die. Subsequently, the obtained sheet was heated at 250° C. for 20 minutes using an infrared heater. The degree of crosslinking of the obtained sheet was 68% in terms of gel fraction.

Sandwich this sheet between 2cm wide iron sheets.
Pressure bonding was carried out at a temperature of 220°C and a pressure of 10 kg/cm ² for 10 minutes. The adhesive strength of the laminate thus obtained is
8.3Kg/2cm, high temperature heat resistance was over 1 hour.

Comparative Example 15 In Example 4, 2,5-dimethyl-2,5
The procedure of Example 4 was repeated except that benzoyl peroxide was used in place of -di-(t-butylperoxy)-hexyne-3. During pelletization using a CCM extruder, the extrudate became flaky and clean pellets could not be obtained.

Comparative Example 16 The same procedure as in Example 4 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 17 The same procedure as in Example 4 was carried out except that maleic anhydride was not added.

The adhesive strength of the obtained laminate was 0.

Comparative Example 18 In Example 4, liquid 1,2-polybutadiene was not added and 2,5-dimethyl-2,5-di-
The same procedure as in Example 2 was carried out except that the amount of (t-butylperoxy)-hexyne-3 added was 0.1 part by weight. The adhesive strength of the obtained laminate is 6.0Kg/2
cm, and high temperature heat resistance was 10 seconds or less.

Comparative Example 19 In Example 4, 2,5-dimethyl-2,5
The procedure of Example 4 was repeated except that -di-(t-butylperoxy)-hexyne-3 was not added. The adhesive strength of the obtained laminate was 0.1Kg/2cm.
High temperature heat resistance was 290 seconds.

Claims (1)

[Claims] 1. Part or all of the polypropylene is grafted with unsaturated carboxylic acids and the gel fraction is 10 to 90.
% crosslinked polypropylene sheet material for lamination. 2 A composition consisting of a modified polypropylene in which part or all of the polypropylene is grafted with unsaturated carboxylic acids, a crosslinking aid, and a radical generator having a half-life temperature of 1 minute higher than the melting point of the modified polypropylene is added to the modified polypropylene. A polypropylene sheet for lamination, which is formed into a sheet at a temperature above the melting point and below the 1-minute half-life temperature of the radical generator, and then heated to a temperature above the 1-minute half-life temperature of the radical generator. How things are manufactured. 3. The manufacturing method according to claim 2, wherein the unsaturated carboxylic acid is maleic anhydride. 4 The crosslinking aid is divinylbenzene or liquid 1.
The manufacturing method according to claim 2, which is 2-polybutadiene. 5. The manufacturing method according to claim 2, wherein the radical generator is dicumyl peroxide or 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3. 6. A composition consisting of polypropylene, unsaturated carboxylic acids, a crosslinking aid, and a radical generator having a 1-minute half-life temperature higher than the melting point of the polypropylene is heated to a temperature higher than the melting point of the polypropylene and lower than the 1-minute half-life temperature of the radical generator. 1. A method for producing a polypropylene sheet for lamination, which comprises forming a sheet into a sheet at a temperature, and then heating to a temperature equal to or higher than the 1-minute half-life temperature of the radical generator. 7. The manufacturing method according to claim 6, wherein the unsaturated carboxylic acid is maleic anhydride or an unsaturated carboxylic acid metal salt. 8 The crosslinking aid is divinylbenzene or liquid 1.
The manufacturing method according to claim 6, which is 2-polybutadiene. 9. The manufacturing method according to claim 6, wherein the radical generator is dicumyl peroxide or 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3.