JPH06228351A - Opaque stretched resin film - Google Patents

Abstract

PURPOSE:To obtain a synthetic paper which does not generate a paper dust causing trouble and has high opaqueness by regulating a stretched film comprising a polypropylene resin and an aromatic polycarbonate resin to have a specific void content and a specific opaqueness. CONSTITUTION:The film comprises as the base material a thermoplastic resin comprising 50-95wt.% polypropylene resin and 50-5wt.% aromatic polycarbonate resin and has a void content calculated using the equation of 20-70% and an opaqueness of 65% or higher. This film has microvoids inside and is useful as a paper for an outdoor poster, label, drafting, adhesive label, etc., and as a substrate for a bar code paper, photographic paper, thermal recording paper, and receiving paper for thermal transfer printing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an opaque stretched resin film having fine pores inside. This opaque resin stretched film is useful as a support for outdoor poster paper, label paper, drafting paper, sticker paper and the like, as well as bar code paper, photographic paper, thermal recording paper and thermal transfer image receiving paper.

[0002]

2. Description of the Related Art A synthetic paper having fine pores inside a film obtained by stretching a thermoplastic resin film containing inorganic fine powder (Japanese Patent Publication No. 46-40794, Japanese Patent Publication No. 60-36173,
Japanese Patent Publication No. 54-31032, US Patent 3773608, US Patent 4
191719) is superior in water resistance, strength, smoothness, etc., as compared with pulp paper, and therefore it is used as a support for labels, election poster paper, thermal recording paper, thermal transfer image receiving sheet, etc. There is. Synthetic paper using these inorganic fine powders as a pore-generating agent by stretching the film has fine pores centered on the inorganic fine powder inside the resin stretched film, and also from the surface of the resin stretched film. Inorganic fine powder protruding and secondary aggregation of this inorganic fine powder (Japanese Patent Laid-Open No. 62-8
7390 gazette), there is a defect that it drops off from the surface of the synthetic paper during printing and white spots occur (so-called pinhole trouble). This blanking is conspicuous and becomes a problem particularly when solid printing / printing in which printing / printing is black. In addition, the inorganic fine powder that has fallen off the surface of the synthetic paper during offset printing mixes into the ink through the blanket, causing the fluidity of the ink to be lost and preventing the proper transfer of the ink from the printing machine to the printing paper. There is a problem that the finish of printed matter is deteriorated (so-called paper dust trouble). As a synthetic paper with less paper dust trouble, a film having a higher melting point than the melting point of the film matrix resin and this matrix resin, and stretching a film based on a mixture of a thermoplastic resin incompatible with the matrix , A synthetic paper having a satin-like appearance composed of a stretched resin film using the high melting point resin as a pore-generating agent has been proposed (US Pat. No. 3,154,461).
U.S. Pat. No. 4,758,462, U.S. Pat. No. 4,438,715, JP-A-59-209849, and JP-B-3-24334). Specifically, these use polypropylene as the matrix of the stretched film, and use polyethylene terephthalate, polybutylene terephthalate, and nylon 6 as the high melting point resin of the pore generating agent.

[0003]

When the pore generating agent is nylon 6, the dispersibility in the polypropylene matrix is poor, the particle size of the nylon 6 particles is as large as 8 to 10 μm, and the pores formed are coarse. Therefore, peko (wrinkles caused by buckling when the stretched film is bent) is likely to occur, which is a problem in practical use. When polyethylene terephthalate or polybutylene terephthalate is used as the pore generating agent, the generation of pores is small and only synthetic paper having an opacity of 65% or less can be obtained. If the stretching temperature is lower than the optimum stretching temperature of polypropylene to increase the opacity of the synthetic paper obtained by increasing the generation of voids, fracture may occur during the stretching of the resin film, or the chuck of the stretching tenter (stretching target) The production efficiency is lowered because the film is detached from the film gripping tool). An object of the present invention is to provide a synthetic paper which has no paper dust trouble and has high opacity.

[0004]

The present invention is a stretched resin film based on a thermoplastic resin containing 50 to 95% by weight of a polypropylene resin and 50 to 5% by weight of an aromatic polycarbonate resin. The resin film has the following formula

[0005]

[Equation 2]

The present invention provides a stretched opaque resin film having pores having a porosity of 20 to 70% calculated in the above and having an opacity of 65% or more. less than,
The present invention will be described in more detail.

[0007]

[Detailed Description of the Invention]

(Polypropylene resin) As polypropylene resin,
A propylene homopolymer, a copolymer of propylene and an α-olefin such as ethylene, butene-1, hexene-1, heptene-1, 4-methylpentene-1 is used. This copolymer may be a random copolymer or a block copolymer. Preferably, melt flow rate (JIS K-7210; 230 ° C, 2.16 kg load)
Is 0.5 to 50 g / 10 minutes, and the crystallinity (X-ray method) is 20.
% Or more, more preferably 40-75%, melting point 150-
190 ° C is good. (Aromatic Polycarbonate Resin) The aromatic polycarbonate resin (A) is produced by reacting an aromatic dihydroxy compound or a small amount of a polyhydroxy compound with phosgene. It is also produced by transesterifying an aromatic dihydroxy compound or a small amount of this polyhydroxy compound with a carbonic acid diester. If necessary, a trifunctional compound as a branching agent and a molecular weight modifier are also provided for the reaction. This aromatic polycarbonate resin is a thermoplastic aromatic polycarbonate which may be branched or unbranched.

Examples of aromatic dihydroxy compounds include:
2,2-bis (4-hydroxyphenyl) propane (hereinafter abbreviated as bisphenol A), tetramethylbisphenol A, tetrabromobisphenol A, bis (4
-Hydroxyphenyl) -p-isopropylbenzene,
Hydroquinone, resorcinol, 4,4′-dihydroxyphenyl, bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis ( 4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ketone, 1,1-bis (4-hydroxyphenyl)
Examples thereof include ethane and 1,1-bis (4-hydroxyphenyl) cyclohexane, and bisphenol A is particularly preferable.

Further, in order to obtain a branched aromatic polycarbonate resin, phloroglucin, 4,6-dimethyl-
2,4,6-tri (4-hydroxyphenyl) heptene-2,4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptane, 2,6-dimethyl-2,
4,6-Tri (4-hydroxyphenyl) heptene-
3,2,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptane, 1,3,5-tri (4-hydroxyphenyl) benzene, 1,1,1-tri (4-hydroxyphenyl) ) Polyhydroxy compounds exemplified by ethane and the like, and 3,3-bis (4-hydroxyaryl) oxindole [= isatin (bisphenol A)], 5-chloroisatin, 5,7-dichloroisatin, 5-bromoisatin and the like are mentioned above. Part of the dihydroxy compound, for example 0.1 to 2 mol%, is replaced by the polyhydroxy compound.

Further suitable monovalent aromatic hydroxy compounds for controlling the molecular weight are m- and p-methylphenol, m- and p-propylphenol, p-bromophenol, p-tertiary-butylphenol and p
-Long-chain alkyl-substituted phenols and the like. A preferred aromatic polycarbonate resin is a bis (4-hydroxyphenyl) alkane-based compound, particularly preferably a polycarbonate containing bisphenol A as a main raw material. A polycarbonate copolymer obtained by using two or more kinds of aromatic dihydroxy compounds in combination and a branched polycarbonate obtained by using a small amount of trivalent phenol compounds can also be mentioned as a suitable example (JP-A-63-30524). Issue 5-6
No. 5328, Japanese Patent Publication No. 55-414, No. 60-25049, Japanese Patent Publication No. 3-4993
No. 0). The aromatic polycarbonate resin may be used as a mixture of two or more kinds.

(Optional component) The film component includes a stabilizer,
You may mix | blend a ultraviolet absorber and a dispersing agent. If necessary,
30% by weight or less of the resin component may be replaced with high density polyethylene, linear low density polyethylene, nylon 6, nylon 6,6, polyethylene terephthalate, polybutylene terephthalate.

(Production of Stretched Film) In the stretched film of the present invention, a resin composition containing polypropylene and aromatic polycarbonate is kneaded using an extruder at a temperature exceeding the melting point of polypropylene, for example, 200 to 300 ° C. Aromatic polycarbonate fine particles (preferably having a particle size of 0.5 to 5 μm) are dispersed in polypropylene by means of the above method, the film is extruded from a die, and then the film is heated to a temperature (for example, 145 ° C.) at which a desired porosity can be obtained. ~
150 ° C) in at least one direction 3.5 to 12 times, preferably in the extruding direction (MD) 3.5 to 5.5 times the width direction (T).
D) Obtained by stretching 4 to 12 times. If necessary, when the stretched film of the present invention is produced, it may be laminated with another resin layer or pulp. Other resin layers include polyolefin resins such as polyethylene and polypropylene, saturated polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 6 and nylon 6,6, polyvinyl chloride,
Examples thereof include polyvinyl resins such as polystyrene.
These resins may contain fillers such as calcium carbonate, titanium dioxide, clay and barium sulfate.

(Stretched Film) This stretched film has a porosity of 20 to 70%, preferably 25 to 60% and an opacity (JIS P-8138) of 65% or more, preferably 80 to 100%. is there. When the porosity is less than 20%, diffuse reflection of light is insufficient and a paper-like feel cannot be obtained. Further, if it exceeds 70%, the strength of the synthetic paper becomes brittle.
If the opacity is less than 65%, the opacity is insufficient, and when printing and binding on this, the characters on the next page show through and the characters appear dull, or in the case of double-sided printing, the printing on the back side It is difficult to see the print / printed surface on the surface. Preferably, the Beck smoothness of this stretched film (JIS P
-8119) is preferably 100 to 10,000 seconds, more preferably 500 to 5,000 seconds, and the wall thickness is 30 to 300 μm. This stretched film itself is used as a poster paper, a drawing paper, or on its surface, a gelatin layer, a heat-sensitive recording coating layer, an image-receiving recording layer is provided, and a photographic paper,
It is useful as a support for use as a thermal recording paper or a thermal transfer image receiving paper.

[0014]

EXAMPLES The present invention will be described below with reference to examples. Example 1 Propylene homocopolymer having a melt index of 4 g / 10 minutes, a melting point of 174 ° C. and a crystallinity of 67% “Mitsubishi Polypro M
A-4 "(trade name of Mitsubishi Petrochemical Co., Ltd.) 80 parts by weight, aromatic polycarbonate" Iupilon S "with a melt index of 8 g / 10 minutes (280 ° C, load 2.16 kg)
-1000 "(manufactured by Mitsubishi Gas Chemical Co., Inc. (trade name)) 20
Parts by weight were mixed, and this mixture was melt-kneaded by a twin-screw kneader (manufactured by Toseki Seimitsu Co., Ltd.) set at 270 ° C., then extruded in a strand form from a die and cooled and cut to obtain pellets. The pellets were melted, compressed and cooled with a press molding machine set at 270 ° C. to obtain a pressed sheet having a length of 120 mm × a width of 120 mm × a thickness of 1.5 mm. This press sheet was heated to 150 ° C. by a small biaxial stretching machine (manufactured by Iwamoto Seisakusho), and then stretched 5 times in the longitudinal direction and 5 times in the transverse direction at the same time, and annealed for 30 seconds to obtain a stretched film. . Table 1 shows the thickness, porosity, opacity, concealment, stretching stability, Beck's smoothness, and the presence or absence of peko of the obtained film. Also,
Cross-sectional grain structure of this stretched film (approximately 3,000 times)
Is shown in FIG.

Measurement method (concealment) Using a pencil hardness tester (scratch tester) manufactured by Toyo Seiki Co., Ltd., a pencil of hardness HB set to be perpendicular to the obtained film was loaded with 200 g of load. And draw a line segment at a speed of 200 seconds / m. The film on which this line segment was drawn was placed on a white paper with an optical density of 0.2 so that the drawing surface was in contact with the white paper surface, and the degree of the line segment that was seen through was visually observed. To judge. Bad: The line segment can be easily read. Good: Difficult or unreadable line segment. (Stability of Stretching) The number of test pieces that have been stretched to the end without breaking or chucking during stretching when 10 test pieces were carried out. (Generation of Peco) 50 from the center of the obtained film
After cutting out two samples each having a size of 100 mm and a width of 100 mm, one is bent into a cylinder with a circumference of 100 mm and the other is bent into a cylinder with a circumference of 50 mm, and then the presence or absence of wrinkles is observed. ◯: No wrinkles occurred on both sheets. △: Only one sheet wrinkles. X: Wrinkles occurred on both sheets.

Examples 2-3 and Comparative Examples 1-10 Stretched films are produced in the same manner as in Example 1 except that the blending and stretching temperatures in Example 1 are changed to those shown in Table 1. Then, the wall thickness, porosity, opacity, concealability, stretching stability, Beck's smoothness, and peko formation were measured.

[0017]

[Table 1]

Example 4 A melt flow rate (MFR) of 85% by weight of a propylene homopolymer "Mitsubishi Polypro FL6S" having a melt flow rate (MFR) of 2.3 g / 10 minutes, a crystallinity of 57% and a melting point of 168 ° C. ) Is 8 g / 10 min (280 ° C.) aromatic polycarbonate “Iupilon S1000” 10% by weight
And high-density polyethylene with a melt flow rate (MFR) of 11 g / 10 minutes (190 ° C) "Mitsubishi Polyech PY"
-20A "5 wt% was blended, and the mixture was melt-kneaded by an extruder set at a temperature of 280 ° C, extruded into a sheet by a die, and cooled to obtain a film. The film was stretched in the machine direction by a factor of 4.5 after being heated by contacting it with a heating roll No. 1. Then, the film was cooled to a temperature of 60 ° C. After heating with hot air at 0 ° C., the film was stretched 9 times in the transverse direction and annealed with hot air at 170 ° C., and then the ears were slit to obtain an opaque stretched resin film, which had good stretching stability. The physical properties of the obtained stretched film were as follows: Thickness: 80 μm Porosity: 27% Opacity: 78% Beck's smoothness: 800 seconds Concealment: Good peko generation: None

Example 5 70 wt% polypropylene (melting point 174 ° C.) having a melt flow rate (MFR) of 0.8 g / 10 min, 20 wt% heavy calcium carbonate having an average particle size of 1.5 μm, and melt flow rate ( A composition comprising 10% by weight of high-density polyethylene having an MFR of 11 g / 10 minutes was prepared by using an extruder.
After melt-kneading at a temperature of 60 ℃, extrude it into a film through a die set at 250 ℃, and cool it to about 60
Cooled to a temperature of ° C. This film again 145 ℃
After heating to the vertical direction, use the difference in the peripheral speed of the rolls to
It was stretched twice. Polypropylene with a melt flow rate of 11 g / 10 min (melting point: 17
2 ° C.) 75% by weight and melt flow rate 8 g / 1
0 minute aromatic polycarbonate (glass transition point 145
25% by weight of the composition was melt-kneaded at a temperature of 270 ° C. using an extruder, extruded into a film form from a T-die, and melt-pressed with a roll to obtain a laminate. This laminate was heated to 155 ° C., then stretched 8.5 times in the transverse direction using a tenter, and annealed at a temperature of 158 ° C. Then, after cooling to 60 ° C., the ear portion was slit to form a three-layer structure (25 μm / 50 μm / 2
An opaque resin stretched film of 5 μm) was obtained. This film was cut into four and a half halves (length 788 mm, width 545 mm),
Offset ink "TSP-4" manufactured by Toyo Ink Mfg. Co., Ltd.
00 "(trade name) and offset 2 manufactured by Mitsubishi Heavy Industries, Ltd.
Using a color printing machine "Diamond Printing Machine" (trade name), 2,000 sheets are printed in two colors, and the number of printed sheets until the adverse effect on the printed sheet due to the ink edge pile on the blanket and the falling paper dust on the blanket (so-called When the number of printable sheets before the occurrence of the paper dust trouble was determined), no sign of the paper dust trouble was observed at 2,000 sheets.

Comparative Example 10 70% by weight of polypropylene (melting point 174 ° C.) having a melt flow rate (MFR) of 0.8 g / 10 min, 20% by weight of ground calcium carbonate having an average particle size of 1.5 μm, and melt flow rate (MFR). 2) was prepared by using an extruder to prepare a composition containing 10% by weight of high-density polyethylene of 11 g / 10 min.
After melt-kneading at a temperature of 60 ℃, extrude it into a film through a die set at 250 ℃, and cool it to about 60
Cooled to a temperature of ° C. This film again 145 ℃
After heating to the vertical direction, use the difference in the peripheral speed of the rolls to
It was stretched twice. Polypropylene with a melt flow rate of 11 g / 10 min (melting point: 17
2%) 60% by weight and a composition of 40% by weight of ground calcium carbonate having an average particle size of 1.5 μm were mixed with an extruder to give 27
The mixture was melt-kneaded at a temperature of 0 ° C., extruded into a film form from a T-die, and melt-pressed with a roll to obtain a laminate. This laminate was heated to 155 ° C., then stretched 8.5 times in the transverse direction using a tenter, and annealed at a temperature of 158 ° C. Then after cooling to 60 ° C,
The ear part is slit to form a three-layer structure (25 μm / 50 μm /
An opaque resin stretched film of 25 μm) was obtained. When the number of printable sheets of this film was evaluated in the same manner as in Example 5, it was 600.

[0021]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it is possible to provide an opaque resin stretched film which is free from paper dust trouble and peko and has excellent hiding power.

[Brief description of drawings]

FIG. 1 shows the particle structure of a cross section of an opaque resin stretched film having microporosity obtained in Example 1 of the present invention.

[Explanation of symbols]

 1 Polypropylene matrix 2 Polycarbonate 3 Voids

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29L 7:00 C08L 23:10 69:00

Claims (1)

[Claims] 1. A resin stretched film based on a thermoplastic resin containing 50 to 95% by weight of a polypropylene resin and 50 to 5% by weight of an aromatic polycarbonate resin, the stretched resin film having the following formula: 1] An opaque resin stretched film having pores having a porosity of 20 to 70% calculated in step 1, and an opacity of 65% or more.