JPS645611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an Al-resin laminate sheet suitable for use as a lithographic plate material and a resin sheet suitable for constituting one layer thereof.

Conventionally, Al (aluminum) plates have been widely used as lithographic plate materials, but as a lithographic plate material that is lighter, easier to handle, and cheaper,
Some of the present inventors have already proposed a laminate of Al foil and a plastic sheet such as polyolefin (Utility Application No. 128850/1982).

However, some problems still remain in the use of the Al-polyolefin laminate sheet as described above as a lithographic plate material. These are, for example, as follows.

B. Since the thermal expansion coefficients of polyolefin sheets and Al foils are different, for example, from this laminated sheet
Deformations such as warping occur due to heating during the process of applying and drying a photosensitive liquid when forming a PS plate.

(b) Deterioration in handling workability due to weak stiffness of the laminated sheet.

(c) Occurrence of blurring of the printed surface due to the easily deformable nature of the polyolefin sheet when installing the printing plate formed from the above-mentioned laminated sheet on a printing machine and during printing.

The main object of the present invention is to solve the above-mentioned problems when using an Al-resin laminate sheet as a lithographic plate material by improving the resin sheet.

As part of achieving the above-mentioned objective, it is also conceivable to blend an inorganic filler into polyolefin in order to obtain a sheet having a coefficient of thermal expansion close to that of Al foil. However, if such an inorganic filler is simply added to polyolefin, the property (flex resistance) that can withstand the bending of the grip and the edge of the grip on the printing machine, which is necessary as a printing substrate, will decrease. cannot be achieved. However, as a result of further research by the present inventors, a sheet of a resin composition in which polyolefin is blended with the above-mentioned inorganic filler and further blended with polyolefin modified with an unsaturated carboxylic acid or a derivative thereof, is It has been found that while having similar coefficients of thermal expansion, it also has excellent strain resistance and deformation resistance, so that an excellent lithographic plate material can be obtained by laminating it with Al foil.

The lithographic plate material of the present invention is based on the above-mentioned knowledge, and more specifically, (a) 20 to 70% by weight of an inorganic filler, (b) 0.5 to 20% by weight of an unsaturated carboxylic acid and/or
or a derivative thereof, and (iii) a laminate sheet in which a resin sheet made of a sheet of a mixture consisting essentially of the remainder polyolefin and an Al layer are laminated. be.

The present invention will be explained in more detail below. In the following descriptions, "%" and "parts" indicate the composition.
are based on weight unless otherwise specified.

(A) Inorganic filler Inorganic fillers are used to lower the thermal expansion coefficient of the resin sheet of the present invention and bring it closer to that of Al foil, but they themselves are usually blended into synthetic resins and rubber. It is something that Such inorganic fillers include Al, Cu, Fe, Ag
Aluminum oxide, its hydrates, aluminum silicate, antimony oxide, barium titanate, colloidal silica, calcium carbonate, barium sulfate, calcium sulfate, iron oxide, asbestos, carbon black , graphite, shirasu balloon, fly ash, glass fiber, calcium silicate, aluminum clay, mica, silica, silica, diatomaceous earth, silicon carbide, talc, zirconium oxide, molybdenum disulfide, titanium oxide, glass bulbs, etc. Examples include compounds, double salts, and mixtures thereof. The shapes of these inorganic fillers include powder (e.g. calcium carbonate), plate (e.g. mica), needle (e.g. asbestos),
They can be spherical (eg, glass-like), fibrous (eg, glass fiber), and the like. Of these,
The powder, plate-like and spherical materials preferably have a diameter of 1 mm or less, and the fibrous materials preferably have a diameter of 1 to 500 microns and a length of 0.01 to 6 mm.

(B) Polyolefin itself is a constituent component of the resin sheet, and polyolefin, which is a raw material for the modified polyolefin described later, includes ethylene or propylene homopolymers, ethylene and propylene copolymers, ethylene and/or propylene. and other α-olefins having up to 7 carbon atoms (the copolymerization ratio of the other α-olefins is up to 20%),
Also, copolymers of ethylene and vinyl compounds such as vinyl acetate, acrylic esters, or methacrylic esters (the copolymerization ratio of the vinyl compound is 50 mol% or less, preferably 40 mol% or less), and the like. Especially low density (0.900g/cm ³ ~)
to high density (~0.980 g/cm ³ ) ethylene homopolymers, propylene homopolymers, ethylene-propylene copolymers and copolymers of ethylene or propylene with other α-olefins are preferably used.

The molecular weight of the polyolefin mentioned above is generally 2
The range is from 10,000 to 1,000,000, preferably from 20,000 to 500,000, and particularly preferably from 50,000 to 300,000.

(C) Modified polyolefin The modified polyolefin used in the present invention is obtained by modifying the above-mentioned polyolefin with an unsaturated carboxylic acid or/and a derivative thereof.

As unsaturated carboxylic acids or derivatives thereof,
Monobasic carboxylic acids having at most 10 carbon atoms and at least one double bond (e.g. acrylic acid, methacrylic acid), dibasic carboxylic acids having at most 15 carbon atoms and at least one double bond (e.g. acrylic acid, methacrylic acid), Examples include maleic anhydride) and anhydrides of the dibasic carboxylic acids (eg maleic anhydride, heimic anhydride). Among these modifiers,
Among these, maleic acid and maleic anhydride are preferably used.

Modified polyolefins are generally obtained by treating polyolefins with a modifier (i.e., unsaturated carboxylic acid or/and its derivatives) in the presence of an organic peroxide, and reaction methods include a solution method, Any known method such as a suspension method or a melting method can be used.

For example, in the case of a solution method, a modified polyolefin can be obtained by adding a polyolefin and a modifier to a nonpolar organic solvent, then adding a radical generator and heating. Non-polar organic solvents used include hexane, heptane, benzene, toluene, xylene, chlorobenzene, and tetrachloroethane. In addition, as a radical generator, 2,5-dimethyl-2,5
-di(tert-butylperoxy)hexane, 2,
Organic peroxides such as 5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and benzoyl peroxide are used. The processing temperature is the temperature at which the polyolefin used dissolves;
A temperature of 110 to 160°C, particularly 130 to 150°C is preferably used.

In addition, when using the suspension method, the polyolefin and the modifier are put into a polar solvent (generally water), the above-mentioned radical generator is added, and the mixture is heated under pressure.
Obtained by processing at temperatures above 100°C.

Furthermore, in the case of a melt method, a modified polyolefin can be obtained by melt-kneading a polyolefin, a modifier, and a radical generator using a melt-kneading machine (for example, an extruder) generally used in the field of synthetic resins. The kneading temperature used is a temperature above the melting point of the polyolefin used and below 300°C, more specifically, 120 to 270°C for polyethylene and 160 to 270°C for polypropylene.
A range of is preferably used.

The amount of modifier used in the production of modified polyolefin is 0.01 to 30 parts per 100 parts of polyolefin.
parts, preferably in the range of 0.1 to 10 parts. If the amount of the modifier used is less than 0.01 part, the effect of use will be poor, and if it exceeds 30 parts, it will not only be difficult to remove unreacted substances but also cause problems such as discoloration, which is not preferable.

(D) Production of resin sheet The resin sheet of the present invention is obtained by forming a composition essentially consisting of the above-described inorganic filler, polyolefin, and modified polyolefin into a sheet.

The composition ratio of the inorganic filler in the composition is 20
~70%, preferably 25-70%, particularly preferably 30
~60%. If the proportion of the inorganic filler is less than 20%, the desired effect of lowering the coefficient of thermal expansion will not be obtained in the obtained sheet, and if it exceeds 70%, the flexibility will decrease and cracks will occur during bending.

In addition, the composition ratio of modified polyolefin is 0.5~
20%, preferably 1-20%, particularly preferably 1-20%
The rate shall be 15%. The composition ratio of modified polyolefin is
If it is less than 0.5%, the effect of improving the stiffness and bending resistance of the product resin sheet will be poor, while if it exceeds 20%, it will be disadvantageous in terms of cost.

On the other hand, polyolefin is used in an amount that essentially constitutes the remainder of the sheet-forming composition of the present invention (however, it does not interfere with the addition of conventional additives as described below), but polyolefin and modified polyolefin The proportion of the modifier in the total amount of is preferably in the range of 0.00006% to 16%, particularly 0.0014 to 3.5%.

The sheet-forming composition further contains anti-aging agents, antioxidants, ultraviolet absorbers, plasticizers, fillers, lubricants, Additives such as flame retardants, antistatic agents and colorants,
It may be added to an extent that does not substantially impair the properties of the composition.

The sheet-forming composition can be obtained by mixing the above components all at once or sequentially. The mixing method is generally a method used in the olefin resin manufacturing and processing industry, such as a dry mixing method using a Henschel mixer, or a melt kneading method using a Banbury mixer, kneader, roll mill, screw extruder, etc. are used in appropriate combinations. At this time, a more uniform composition can be obtained by further melt-kneading the mixture that has been dry mixed or melt-kneaded. Generally, the composition is melt-kneaded, formed into pellets, and then subjected to sheet formation.

The resin sheet of the present invention can be obtained by forming the sheet-forming composition obtained as described above into a sheet using a sheet extrusion device, a calender device, etc. that are commonly used in the polyolefin industry. The thickness of the sheet is usually 0.05 to 0.5 mm.
If it is less than 0.05 mm, there is a risk that the plate will stretch during printing, and if it exceeds 0.5 mm, it will lose its price advantage.

The laminated sheet of the present invention is obtained by laminating an Al layer on the resin sheet of the present invention obtained as described above. As shown in FIG. 1, the laminated sheet A is a resin sheet 1 obtained as described above.
By directly forming an Al layer 2 on one surface by means such as vapor deposition, or by bonding the resin sheet 1 and Al foil 2a with an adhesive 3 as shown in FIG. You can get it by twisting it.

As the adhesive 3, it is preferable to use a urethane-based or rubber-based adhesive.

Aluminum layer 2, 2a in laminated sheet
is generally subjected to graining for plate making, so it is desirable to have a thickness of at least 6 μm or more.
The upper limit is not particularly critical, but is generally 200μ or less.

In order to obtain a lithographic printing plate using the laminated sheet of the present invention as a plate material, the same operations as those for conventional Al plate materials may be performed on the Al side thereof. For such operations, graining; if necessary, surface treatment (cleaning the surface of the plate material with a weak acid solution, etc.) is performed, and then a mixture of sodium silicate and potassium silicate is used. Surface oxidation treatments such as 5% hot solution treatment, anodic oxidation treatment, zirconium fluoride treatment, and calcium nitrate solution treatment; photosensitive liquid coating and drying are included, and a PS plate is obtained by this process. The thus obtained PS plate is further subjected to treatments such as exposure, oil sensitization, development, and oil desensitization to obtain a lithographic printing plate.

In addition, the above method can also be achieved by modifying the above method and applying the photosensitive liquid to the Al foil and drying it, and comparing the obtained photosensitive liquid coated Al foil with the resin sheet of the present invention using an adhesive. A PS plate similar to that can be obtained, and a similar lithographic printing plate can also be obtained using this.

As described above, according to the present invention, there is provided a resin sheet which has a low coefficient of thermal expansion and is excellent in stiffness and deformation resistance, and is made of a polyolefin and a polyolefin modified with an unsaturated carboxylic acid or a derivative thereof in addition to an inorganic filler. Moreover, by laminating this with an Al foil or layer, an Al resin laminated sheet having excellent suitability as a lithographic plate material is provided.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 Polypropylene homopolymer (melt flow
index 2g/10 min) 35%, polypropylene homopolymer (melt flow index 20
g/10 min) of maleic anhydride modified product (maleic anhydride content 0.4%) and talc with an average particle size of 2μ.
A sheet having a thickness of 0.2 mm was produced by melt-kneading a composition consisting of 55% using an extruder.

The coefficient of linear expansion of the obtained sheet was 3×10 ^-5 (1/℃)
It was hot. By the way, the coefficient of linear expansion of a sheet made of a single polypropylene homopolymer is 12×10 ^-5 1/℃
That of Al foil (thickness 30μ) was 2.7×10 ^-5 1/°C.

Next, we measured the tensile strength and elongation rate, and found that the tensile strength of the sheet obtained above was
The weight was 350Kg/cm ² and the elongation rate was 5%. On the other hand, the strain strength of Al foil (thickness 30μ) is 520Kg/cm ² ,
The elongation rate was 3%.

From the above measurement results, it was found that the linear expansion coefficient and strain elongation rate of the sheet obtained above were close to the linear expansion coefficient and strain elongation rate of Al foil.

Next, the polypropylene sheet obtained above and
PS made by laminating Al foil (30 μ) using 7 g/m ² of urethane adhesive, graining and anodizing the aluminum surface, and uniformly applying 2.5 g/m ² of PS photosensitive liquid. I made a plate, but it warped during the manufacturing process.
No deformation was observed, and printability on a printing press was good.

Furthermore, the bending radius of the above laminated plate material is 5.
A test was conducted in which the Al foil was bent at 180 degrees, but no cracks occurred in the Al foil.

Example 2 Polypropylene homopolymer 40 used in Example 1
A sheet having a thickness of 0.2 mm was prepared in the same manner as in Example 1 using a composition consisting of 10% modified polypropylene and 50% mica powder having an average particle size of 10 μm.

The coefficient of linear expansion of this sheet was 2.5×10 ⁻⁵ (1/° C.), which was close to that of Al foil. Moreover, the tensile elongation rate was 3%, which was the same as that of Al foil.

Next, the polypropylene sheet obtained above and
PS made by laminating Al foil (30 μ) using 7 g/m ² of urethane adhesive, graining and anodizing the aluminum surface, and uniformly applying 2.5 g/m ² of PS photosensitive liquid. The plate was made, but during the manufacturing process there were warpages,
No deformation was observed, and the printability on the printing press was good.

Furthermore, the bending radius of the above laminated plate material is 5.
A test was conducted in which the Al foil was bent at 180 degrees, but no cracks occurred in the Al foil.

Comparative Example 1 A sheet with a thickness of 0.2 mm was produced in the same manner as in Example 1 except that the modified polypropylene was not used and a 45% polypropylene homopolymer was used instead.

The coefficient of linear expansion of this sheet was 5×10 ^-5 1/°C.

On the other hand, apply urethane adhesive 7 to one side of this sheet.
When the aluminum foil with a thickness of 30 μm was bent at 180 degrees with a bending radius of 5 mm using the aluminum foil with a thickness of 30 μg/m ² , cracks appeared in the aluminum foil.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are respectively cross-sectional views in the thickness direction of embodiments of the lithographic plate material of the present invention. 1...Resin sheet, 2...Al vapor deposition layer, 2a...Al foil,
3...Adhesive layer.

Claims (1)

[Scope of Claims] 1 (A) (a) 20 to 70% by weight of an inorganic filler, (b) 0.5 to 20% by weight of a polyolefin modified with an unsaturated carboxylic acid and/or its derivative, and A lithographic plate material comprising: (c) a resin sheet made of a sheet of a mixture consisting essentially of the remainder of the polyolefin; and (B) a laminate sheet, which is a laminate with an Al layer.