JP2001081206A - Transparent sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare transparent sheet which has a good transparency, blocking resistance and smoothness, requires no powdery surface modifier and shows a good printability. SOLUTION: This transparent sheet comprises a composition which essentially comprises a propylene polymer and has a nucleating agent content of from 0.1 to 0.8 wt.%, an anti-blocking agent content of from 0.01 to 0.3 wt.% and a total content of the anti-blocking agent and a lubricant of from 0.01 to 0.3 wt.%. The composition further contains from 0.01 to 0.3 wt.% antistatic agent. Furthermore, each surface has a different surface smoothness, and when the surfaces having a higher and a lower surface smoothness are termed as a gloss surface and a non-gloss surface, respectively, the non-gloss surface has a gloss of 140% or smaller, and the difference of gloss between the gloss surface and the non-gloss surface is from 5 to 20%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent sheet made of plastic, which has excellent transparency and hardly causes blocking even when a plurality of sheets are laminated.

[0002]

2. Description of the Related Art Plastic transparent sheets are used for cosmetic transparent cases, stationery transparent cases, stationery files, blister packs and the like. Conventionally, transparency has been improved by smoothing the sheet surface. Specifically, for example, when performing extrusion molding by the T-die method, a molded body extruded from the T-die is sandwiched between a main roll and a drive roll to be processed into a thin sheet, and further, the main roll is By sandwiching the mirror between a mirror-finished ring-shaped stainless steel belt provided at the subsequent stage of the driving roll, the thickness of the sheet is made uniform and both sides of the sheet are mirror-finished. This method is called an endless belt method because the stainless steel belt has a ring shape. However, if the surface of the belt is processed to be smooth, when the transparent sheets are laminated, adjacent ones are likely to adhere to each other, so-called blocking. Also, the slipperiness is reduced. Therefore, by attaching a powdery surface modifier such as starch to the sheet surface,
Improvements were being made.

[0003]

However, when performing sheet-fed printing, it is necessary to remove a powdery surface modifier such as starch, and the operation is troublesome. Further, if the removal of the powdery surface modifier is insufficient, there is a problem that the printability is reduced. The present invention has been made in view of the above circumstances, a transparent sheet having good transparency, and anti-blocking properties, good slipperiness, a transparent sheet that does not need to use a powdery surface modifier. The task is to provide. Further, another object is to provide a transparent sheet having good printability.

[0004]

In order to solve the above-mentioned problems, the present invention provides the following means. The first invention comprises a propylene-based polymer as a main component,
When the content of the nucleating agent is 0.1 to 0.8% by weight, the content of the antiblocking agent is 0.01 to 0.3% by weight, and the total content of the slipping antiblocking agent and the lubricant is 0.0
A transparent sheet comprising 1 to 0.3% by weight of a composition. A second invention is the transparent sheet according to the first invention, wherein the composition contains 0.01 to 0.3% by weight of an antistatic agent. According to a third aspect, in the transparent sheet according to the first or second aspect, when the surfaces having high and low surface smoothness are different from each other, the surfaces having high and low surface smoothness are defined as a glossy surface and a non-glossy surface, respectively. Is a transparent sheet having a gloss of 140% or less and a gloss difference between the glossy surface and the non-glossy surface of 5 to 20%. A fourth invention is the transparent sheet according to any one of the first to third inventions, wherein the haze is 2 to 15%. A fifth invention is the transparent sheet according to any one of the first to fourth inventions, wherein the surface specific resistance is 10 ¹⁴ to 10 ¹¹ Ω-cm.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The propylene-based polymer used in the present invention includes propylene homopolymer, propylene and other α-olefins of not more than 20% by weight, for example, ethylene, butene 1,4-methylpentene-1 octene. -1
For example, a random copolymer with the like is used. The random copolymer may be a mixture of two or more of these comonomers. These propylene polymers may be used alone or in combination of two or more. In the present invention, propylene and other α
Since a block copolymer with an olefin cannot provide good transparency, a homopolymer of propylene, a random copolymer of propylene with another α-olefin, or the like is preferable.

When the content of the nucleating agent is less than 0.1% by weight, transparency cannot be obtained, and when it exceeds 0.8% by weight, the effect of improving transparency is saturated. A nucleating agent is a substance that has an effect of growing a crystal as a crystal nucleus when added to a crystalline resin such as polypropylene in the field of synthesis, and various substances are known. Examples thereof include metal salts of carboxylic acids, dibenzylidene sorbitol derivatives, alkali metal phosphate salts, and inorganic compounds such as talc. Specific examples include sodium benzoate, aluminum adipate, aluminum-pt-butylbenzoate, 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-bis- (p-ethylbenzylidene) Sorbitol, 1,3-p-chlorobenzylidene 2,4-p-methylbenzylidene sorbitol, sodium-bis- (4-t-methylphenylphosphate), potassium-bis- (4,6-di-t-butylphenyl) ) Phosphate, sodium 2-2′-methylene-bis- (4,6-di-t-butyl) phosphate,
Sodium-2-2'-ethylidene-bis- (4,6
-Di-t-butylphenyl) phosphate, as well as talc, calcium carbonate and the like. Also, high density polyethylene or the like can be used.

[0007] The anti-blocking agent is 0.01 to
0.3% by weight or more is used. If it is less than 0.01% by weight, the blocking property is reduced. The total content of the antiblocking agent and the lubricant in the composition is 0.01% by weight.
If the amount is less than the above, blocking resistance and slipperiness decrease.
If the amount exceeds 0.3% by weight, these additives may exude to the sheet surface, and the printability may be reduced. Therefore,
The upper limit of the amount of the antiblocking agent is 0.3% by weight.
The upper limit of the amount of the lubricant is 0.029% by weight.

The anti-blocking agent is added for the purpose of improving the blocking resistance and the slipperiness of a molded plastic product. The lubricant is a processing aid added at the time of molding for the purpose of improving fluidity, thermal stability, and the like. Anti-blocking agents and lubricants
Generally, hydrocarbon lubricants (liquid paraffin, paraffin wax, etc.), fatty acid lubricants, higher alcohol lubricants (stearic acid, stearyl alcohol, etc.), amide lubricants (stearic acid amide, oleic acid amide, etc.), ester lubricants (stearic acid) Butyl, glyceride stearate, etc.), metal soap-based lubricants (calcium stearate, zinc stearate, etc.) and the like. Some of these materials have both anti-blocking and lubricating properties. Therefore, in the present invention, the anti-blocking agent and the lubricant are not necessarily used.
There is no need to add more than one substance.

In the present invention, silica, talc and the like are preferably used as the antiblocking agent.
As the lubricant, specifically, stearic acid amide, oleic acid amide and the like are preferable.

As described above, the transparent sheet of the present invention has a propylene polymer as a main component and a nucleating agent content of 0.1.
0.8% by weight, and the content of the antiblocking agent is 0.1%.
Since the composition is 0.01 to 0.3% by weight and the total content of the antiblocking agent and the lubricant is 0.01 to 0.3% by weight, the transparency is good, and the blocking resistance of the transparent sheet itself is good. It has good slipperiness and does not require the use of a powdery surface modifier as in the prior art. Therefore, it has excellent printability, and is particularly suitable for applications such as sheet-fed printing.

When the antistatic agent is added to the composition of the transparent sheet of the present invention in an amount of 0.01 to 0.3% by weight, the surface resistivity of the transparent sheet can be reduced. As a result, the fixability of the printing ink is improved, and the printability can be improved. If the amount is less than 0.01% by weight, a sufficient effect cannot be obtained. If the amount exceeds 0.3% by weight, the antistatic agent may seep out to the sheet surface, and the printability may be reduced. In order to obtain a good printability, specifically, so that the surface resistivity is ^{10 14 ~10 1 1 Ω-cm} , when adjusting the amount of the antistatic agent added preferably. 10 ¹⁴ Ω
-cm exceeds 10 ¹¹ Ω-cm
It is difficult to make the amount less than the above by adding an antistatic agent.
The surface resistivity is a value measured according to JIS K6911.

Examples of the antistatic agent include anionic surfactants (such as alkyl sulfonates and alkyl sulfates), cationic surfactants (such as alkyltrimethylammonium salts, acyloylamide propyltrimethylammonium methosulfate), and amphoteric surfactants. Agents (alkylbentine type, imidazoline type, etc.), nonionic surfactants (fatty acid alkylol amide, fatty acid glycerin ester, etc.) and the like are used. In the present invention, nonionic surfactants are preferred, and more specifically, glycerin monostearate, aliphatic amines and the like are preferred.

The composition of the material for the transparent sheet of the present invention may include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), etc. in order to improve the heat sealability according to the application. , 30% by weight or less. In addition, if necessary, various conventional additives such as an antioxidant, a weather resistance stabilizer, a pigment, a softener and the like can be added within a range not to impair the effects of the present invention.

The transparent sheet of the present invention can be obtained by molding the above composition by various methods. Examples of the molding method include an extrusion molding method using a T-die, an air-cooled inflation method, an air-cooled two-stage cooling inflation method, and a water-cooled inflation method. In the extrusion molding method, for example, an air knife system in which high-speed air is blown with an air knife to cool immediately after being formed into a sheet by sandwiching a molded body extruded from a T-die between a main roll and a driving roll, and is preferable. Further, an endless belt system can be used.

Further, in the transparent sheet of the present invention, when the surfaces having high and low surface smoothness are different from each other, the glossy and non-glossy surfaces are respectively 140. % Or less, and the difference in gloss between the glossy surface and the non-glossy surface is preferably 5 to 20%, more preferably 1 to 20%.
0 to 20%. Gloss is a measured value obtained according to JIS Z8741. The difference in the surface smoothness of both surfaces can be specifically given by a method of providing a difference in the surface smoothness of the cooling rolls on the outer surface and the inner surface when forming the sheet, or a method of providing a difference in the cooling speed. By making the surface smoothness of both surfaces different as described above, when a plurality of transparent sheets are laminated, the glossy surface and the non-glossy surface come into contact with each other, so that the blocking resistance and the slipperiness can be improved. If the gloss of the non-glossy surface is less than 140%, the transparency may decrease. If the difference in gloss between the glossy surface and the non-glossy surface is less than 5%, the effect of improving blocking resistance and slipperiness is insufficient, and if it exceeds 20%, transparency may be reduced.

The thickness of the transparent sheet of the present invention is generally about 0.05 to 3 mm. Those having a thickness of less than 0.05 mm are difficult to manufacture, and exceeding 3 mm may reduce the transparency or limit the application. The haze (JIS K 6714) of the transparent sheet of the present invention is 2 to 15
%. If it is less than 2%, the coefficient of sliding friction is insufficient, and if it exceeds 15%, the transparency is poor and the product value is reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Various compositions (MFR indicates melt flow rate) shown in Table 1 were molded using an extruder shown in Table 1 to obtain a transparent sheet. Table 1 also shows the properties of these transparent sheets.

The nucleating agent is a sorbitol nucleating agent, the antiblocking agent (AB agent) is silica,
Erucic acid amide was used as a lubricant, and glycerin monoester was used as an antistatic agent. The blocking degree was determined by laminating 20 sample pieces (10 cm × 10 cm), applying a load of 5 kg in a 40 ° C. atmosphere for 24 hours, observing the blocking state (degree of adhesion) by visual observation, It was confirmed by observing the state when the film was actually peeled off by hand. Printability was evaluated by performing gravure printing, and visually confirming the printing state.

[0019]

[Table 1]

As can be seen from Table 1, all of Examples 1 to 3 were excellent in transparency, blocking resistance and printability. On the other hand, in Comparative Example 1, the transparency was poor because no nucleating agent was added, and in Comparative Example 2, the total content of the lubricant and the antiblocking agent exceeded 0.3% by weight. Printing unevenness has occurred. In Comparative Example 3, since the gloss on both sides was large, the coefficient of friction could not be measured, and blocking occurred. In Comparative Example 4, since the antistatic agent was not added, the surface resistivity increased, and the printability was poor. In Comparative Example 5, printing unevenness occurred because starch powder was present on the sheet surface.

[0021]

As described above, the transparent sheet of the present invention contains a propylene polymer as a main component, has a nucleating agent content of 0.1 to 0.8% by weight, and an antiblocking agent content of 0.1 to 0.8% by weight. 0.01 to 0.3% by weight, and the total content of the antiblocking agent and the lubricant is 0.01 to 0.3% by weight.
, The transparency is good, the blocking resistance and the slipperiness of the transparent sheet itself are good, and it is not necessary to use a powdery surface modifier as in the prior art. Therefore, it has excellent printability, and is particularly suitable for applications such as sheet-fed printing.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/10 C08L 23/10 (72) Inventor Fumio Saito 4-1 Nihonbashi Kobunacho, Chuo-ku, Tokyo Heisei Heisei F-term in Polymer Co., Ltd. (Reference) 4F071 AA16 AA20 AA71 AB21 AB30 AC05 AC09 AC10 AC12 AC15 AE10 AE11 AE16 AE22 AF30 AF32Y AF53 BC01 4J002 AE033 AE053 BB032 BB121 BB141 BB151 DE236 DJ046 EC056 EC0006 EG077 EF077 EW046 FD202 FD203 FD206 FD207 FD318 GC00 GG00

Claims (5)

[Claims] 1. A propylene polymer as a main component, a nucleating agent content of 0.1 to 0.8% by weight, an antiblocking agent content of 0.01 to 0.3% by weight, and The total content of the antiblocking agent and the lubricant is 0.01 to
A transparent sheet comprising 0.3% by weight of a composition. 2. The transparent sheet according to claim 1, wherein
A transparent sheet, wherein the composition contains 0.01 to 0.3% by weight of an antistatic agent. 3. The transparent sheet according to claim 1, wherein both surfaces have different surface smoothness, and a surface having a high surface smoothness and a surface having a low surface smoothness are a glossy surface and a non-gloss surface, respectively.
A transparent sheet wherein the gloss on the non-glossy surface is 140% or less, and the difference in gloss between the glossy surface and the non-glossy surface is 5 to 20%. 4. The transparent sheet according to claim 1, wherein the transparent sheet has a haze of 2 to 15%. 5. The transparent sheet according to claim 1, which has a surface resistivity of 10 ¹⁴ Ω to 10 ¹¹ Ω.
-Transparent sheet characterized by being -cm.