JPH043774B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyolefin sheet for decorative laminates, which has extremely little whitening phenomenon (hereinafter abbreviated as ruled line whitening) that occurs at the hinge part when bent after being subjected to ruled line processing at room temperature, and which has good weldability. Sheets of polypropylene (propylene homopolymers and copolymers with a small amount of ethylene, etc.) have good hinge properties, so they can be used for stationery and light electrical products that require cosmetics, such as hard cases such as file cases and letter files. It has come to be used for packaging supplies. Performance when used in these applications is: (1) It must have rigidity and impact resistance above a certain level, (2) It must have hinge characteristics and do not impair cosmetic appearance due to whitening of lines, etc. ) Good weldability using ultrasonic waves or hot air is required. However, propylene homopolymer (hereinafter referred to as homopolymer)
PP) has poor impact resistance (especially at low temperatures), and propylene/ethylene random copolymer (hereinafter referred to as random PP) has low rigidity, so both were unsuitable for the above applications. . Furthermore, propylene/ethylene block copolymer (hereinafter abbreviated as block PP) has a good balance of rigidity and impact resistance, but its commercial value is significantly reduced because the ruled lines tend to whiten. In order to prevent whitening of the lines, a method of processing the lines using a blade heated to 100 to 160℃ (hereinafter referred to as
(thermal creasing) has been adopted. However, in this thermal creasing process, there is a difference in thermal expansion coefficient between the steel creasing blade and the plywood board, so if the creasing blade and punching blade (Thomson blade) are combined together, the temperature will rise. During repeated descents, gaps occur, and polypropylene sheets processed with a high-temperature creasing blade shrink when cooled. Therefore, it is necessary to perform the creasing process and the punching process separately, and as a result, it takes time to align the two processes, and there is a problem in that dimensional accuracy decreases due to positional deviation. . On the other hand, creasing at room temperature is generally done with a combination of a steel creasing blade with a semicircular cross-section and a thickness of 0.2 to 3.0 m/m and a commercially available Thomson blade, all built into a single plywood base. By using a mold and pressing it against the sheet, there is no deviation between punching and creasing, and a highly accurate ruled product can be obtained. It is desired that a sheet subjected to room-temperature creasing be made of a material that satisfies market requirements in terms of rigidity and impact resistance, and that does not cause whitening of the creasing, but such a polypropylene sheet has so far not been found. In addition, for products for the above-mentioned purposes, it is necessary to overlap the sheets and join them by welding such as ultrasonic welding or hot air welding after the ruled line bending process. Moreover, the welding must be done uniformly and without damaging the appearance after joining, but if the welding temperature is too high in the case of ultrasonic or hot air welding, contact with heat jigs such as horns and anvils may occur. It is desirable to be able to weld at as low a temperature as possible, since the marks caused by the welding may become glossy (hereinafter referred to as "terry"), which is a problem in terms of appearance, or may cause recesses. The purpose of the present invention is to create a hard case or letter file for use as a decorative case, which has extremely little whitening of ruled lines due to room-temperature ruled line processing from a sheet shape, has good low-temperature weldability, and has excellent mechanical properties such as rigidity and impact resistance. An object of the present invention is to provide a polyolefin in sheet for decorative laminates used in the production of etc. In accordance with the present invention, (A) 30-80% by weight of a propylene/ethylene random copolymer having an ethylene content of 10% by weight or less; (B) 10-50% by weight of polyethylene having a density of 0.94 g/cc or more; (C) A polyolefin sheet for decorative laminates is provided, which is formed by extruding a resin composition comprising 0 to 40% by weight of propylene homopolymer into a sheet shape. In the present invention, the propylene/ethylene random copolymer (hereinafter abbreviated as random PP), which is component A, is a copolymer made from a mixture of monomers (ethylene and propylene), and is a copolymer made from a mixture of monomers (ethylene and propylene). It also includes those obtained by polymerization and those obtained by performing multistage polymerization by changing the supply ratio of the monomer mixture. Ethylene content is 10% by weight or less, preferably 2
~5% by weight of random PP is used. When the ethylene content is more than 10% by weight, the rigidity decreases significantly, making it unsuitable for use in letterfiles and hard cases. In the production of random PP, a multi-stage polymerization method is used to improve the balance of physical properties. In the polymerization stage, when the ethylene/propylene monomer ratio is 3/1 to 1/3, a rubbery substance (hereinafter abbreviated as rubber) is produced. When this rubbery substance is included in random PP, a good balance between rigidity and impact resistance is achieved. However, if the content of this rubbery substance increases, whitening of ruled lines tends to be noticeable, so it is desirable that the content of this rubbery substance in the resin composition is 5% by weight or less. Particularly preferred random physical properties used in the present invention
PP can be obtained by prepolymerizing propylene monomer and further polymerizing a propylene/ethylene mixed gas having an ethylene mixing ratio of 10% by weight or less. In addition to the ethylene homopolymer, the B component polyethylene (hereinafter abbreviated as PE) is a copolymer of ethylene with α-olefin such as propylene and butene (as a result of copolymerization with α-olefin). , with a total methyl group concentration of 0 to 30/1000 carbons). Also, the density is
Use 0.94g/cc or more. If the density is less than 0.94, the rigidity is low and the desired sheet cannot be obtained. Furthermore, the melt index (hereinafter abbreviated as MI) of the random PP of the A component and the homo PP of the C component is not particularly limited, but is 0.3 to 10 g/10 min.
It is preferable that When MI is less than 0.3 g/10 min, kneading properties with other resins are poor and extrusion processability is reduced. On the other hand, if it exceeds 10g/10min, sagging during extrusion will be large, sheeting properties will be poor, and the impact resistance of the sheet will decrease, making it easy to crack when it is made into a product. Further, the MI of PE as component B is preferably 0.2 to 5 g/10 min for the same reason. The blending ratio of the above three resins is random for component A.
30-80% by weight of PP, preferably 40-75% by weight;
PE of component B is 10 to 50% by weight, preferably 15 to 40%
Weight %: HomoPP as component C is in the range of 0 to 40 weight %, preferably 0 to 35 weight %. If the blending ratio of random PP as component A is less than 30%, the anti-whitening effect will be insufficient, while if it exceeds 80% by weight, rigidity will be insufficient. If the blending ratio of component B is less than 10%, the impact resistance will be insufficient, while if it exceeds 50%, the welding strength will tend to be weakened and the bending strength of the hinge will decrease. If the blending amount of C-component homo-PP exceeds 40%, the impact resistance will decrease, and the welding strength will be weak under normal conditions when using a commercially available welding machine for ultrasonic welding or hot air welding. There is a tendency to Pigments, various stabilizers, antistatic agents, etc. can be further added to the above resin composition according to conventional methods. In addition, pyrolytic foaming agents (e.g., azodicarboxylic acid amide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, etc.) and blowing aids (e.g., urea, zinc oxide, zinc stearate, etc.) are added to form foam sheets. It is also possible to do this. The composition is usually heated and kneaded using an extruder, extruded from a die such as a T-die or a circular die, and then formed into a sheet shape by cooling with rolls or air. At this time, the surface may be embossed with a pressure roll. . The machine and method used to form the sheet shape may be conventional machines and are not particularly limited. The crease processing method uses a mold that incorporates a Thomson blade and a crease blade into a single plywood board, as described above, and uses a regular mechanical press (Die Press, Victoria, etc.) or a hydraulic press to create a sheet with the length of the crease blade.
This may be done by pressing with a force of 0.1 to 2 ton/cm, preferably 0.5 to 1 ton/cm. The sheet according to the present invention has extremely little whitening of ruled lines. Therefore, hard cases, letter files, etc., which are used as decorative cases and which do not suffer from the whitening phenomenon, can be easily obtained with good dimensional stability by simultaneously performing punching and creasing at room temperature. The joining of sheets for decorative laminates is normally required to be performed using a general commercially available welding machine such as ultrasonic welding or hot air welding. Ultrasonic welding is a method in which stacked sheets are pressed together using a horn and an anvil, oscillating ultrasonic waves, and the joint surfaces between the sheets are softened and melted by heat generated by local vibrations, thereby joining the sheets. Some of the sheets obtained when conducting studies with the goal of preventing whitening had poor low-temperature melting properties or too high thermal conductivity. However, in the case of the sheet according to the present invention, this problem has been eliminated and sufficient welding strength can be achieved without damage due to welding using a commercially available ultrasonic welding machine. is obtained. Hot air welding is a method in which the amount of hot air at 250° C. to 500° C. is adjusted, and the bonded portion of the sheet is passed through a hot air blowing section to soften and melt, and then pressed and bonded. The sheet according to the present invention could easily be welded to sufficient strength without being damaged by this method. In the Examples, physical property values were measured in accordance with the following method. Ethylene content in PP random copolymer: Infrared absorption spectrum of press-molded film
Measure the absorbance at 720, 726, and 730 cm ^-1 and calculate using a conventional method. Methyl group concentration: Measure the absorption at 1378 cm ^-1 due to the bending vibration of the amount of methyl in the infrared absorption spectrum of the press-molded film, and the overlapping absorption at 1369 and 1353 cm ^-1 of methylene groups, and calculate by a conventional method. Density: Measure the molded sheet according to JIS K-6758. MI: Measured according to ASTM D-1238-62T. Rigidity: Judged based on flexural modulus. The flexural modulus is
JIS K for press-formed sheets with a thickness of 6m/m
-Measure according to 7203. Dupont impact strength: Measured using a Dupont impact tester manufactured by Toyo Seiki Co., Ltd. on a sheet having a thickness of 0.8 m/m. A striking core with a radius of curvature of 1/2 inch at the tip was used, and the values were expressed as non-destructive-destructive energy values at 23°C. Line whitening: Rule line whitening was determined visually. ◎No whitening ○Slight whitening △Conspicuous whitening ×Significant whitening The present invention will be specifically explained below with reference to Examples and Comparative Examples. Example 1 30 parts by weight of homo PP with MI of 1.5 g/10 min and 4% ethylene content with MI of 1.5 g/10 min
Random PP (random PP produced by prepolymerizing propylene and further polymerizing ethylene-propylene mixed gas with an ethylene mixing ratio of 6% by weight)
with a density of 0.96 g/cc and an MI of 0.3 g/cc.
0.6 parts by weight of black pigment was added to a resin composition consisting of 30 parts by weight of PE at 10 min, and the mixture was thoroughly stirred using a Henschel mixer.
Using an extruder with φ and L/D of 22, heat and knead at a cylinder maximum temperature of 220°C, extrude through a T-die with a lip length of 150mm, and form while cooling with a take-up roll to a thickness of 0.8mm. A sheet sample with a width of 120 mm was produced. The physical properties of this sheet are shown in Table 1.
It sufficiently met the market requirements of 8000 Kg/cm ² in flexural modulus and 15 to 20 Kgcm in Dupont impact strength, which are standard market requirements for use in cosmetic cases, letter files, etc. A commercially available creasing blade with a thickness of 0.8 mm and a nearly semicircular tip was used at room temperature to crease the sheet using a hydraulic die press. The thickness of the hinge after processing was adjusted to 0.2 mm.
When folded along the ruled lines, almost no whitening occurred and the result was good. In a folding durability test by repeatedly bending the ruled line portion, no breakage or cracking occurred even after 10,000 bends on 5 test pieces. The sheets were overlapped and a welding test was performed using an ultrasonic welder. The anvil has a tip shape of 1.5mmφ
10 points were used. Amplitude 50μ, pressing force 5
Kg/cm ² , oscillation time is 0.3 seconds, and the joint peel strength at two points is 4Kg, which is sufficient strength for practical use.Moreover, there is little trough on the horn (smooth surface) side of the weld, and it has a good appearance. There was no loss in product value. Comparative Example 1 75 parts by weight of a propylene/ethylene block copolymer with a resin composition MI of 1.5 g/10 min and an ethylene content of 8% and a density of 0.96 g/cc and an MI of 0.3.
The procedure was the same as in Example 1, except that 25 parts by weight of PE was used, which was 25 g/10 min. A similar evaluation was performed on the obtained sheet, and the bending elastic modulus was 12000 kg/
The Dupont impact strength in cm ² was 40 to 45 Kg·cm, indicating a good balance of physical properties. However, when this sheet was subjected to a creasing process at room temperature, the whitening of the criss-crossed lines appeared sharply when folded, resulting in an unsightly appearance. Examples 2 to 8 and Comparative Examples 2 to 8 Samples were prepared and evaluated in the same manner as in Example 1, except that the components and composition ratios of homo PP, random PP, and PE were changed as shown in Tables 1 and 2. .
Note that the rough quality of each component is shown in Table 3. In Examples 2 to 6, in which the composition ratio of each component was changed within the range of the present invention, physical properties such as rigidity and impact strength were well balanced without causing any practical problems. On the other hand, Comparative Example 2, which is made of homo PP alone, has problems in impact strength and welding, and Comparative Example 3, which is made of random PP alone, has low rigidity and is also insufficient in terms of impact strength. Comparative Example 4, which is a 50/50 blend of both, has an improved physical property balance than Comparative Example 2, but is insufficient in impact strength. On the other hand, in Comparative Example 5, which is a 40:60% by weight blend of random PP and PE, the impact strength is extremely good due to the large amount of PE, but the bending strength tends to be weak and the weldability is also poor. In Comparative Example 6 using 50 parts of homo PP, 10 parts of random PP, and 40 parts of PE, weldability was poor and whitening was noticeable. In Example 7, in which random PP with an ethylene content of 8% was used, a slight decrease in rigidity was observed compared to Example 1, but there was no problem in practical use. but,
When random PP with an ethylene content of more than 10% was used (Comparative Example 7), the rigidity was significantly reduced. Further, in Example 8 in which PE with a density of 0.95 g/cc was used, a decrease in rigidity was observed compared to Example 1, although this was within a practical range. On the other hand, the density
When using 0.93g/cc (Comparative Example 8)
was unsuitable due to a significant decrease in rigidity.

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Claims (1)

[Scope of Claims] 1 (A) 30-80% by weight of a propylene/ethylene random copolymer having an ethylene content of 10% by weight or less, and (B) 10-50% by weight of polyethylene having a density of 0.94 g/cc or more. and (C) propylene homopolymer 0
A polyolefin in-sheet for decorative laminates made by extruding a resin composition containing up to 40% by weight into a sheet. 2. A polyolefin insheet for a decorative board according to claim 1, which is used for manufacturing a hard case or letter file having a hinge portion formed by ruled lines.