JPS6349701B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene resin composition particularly suitable for producing translucent polypropylene films.

Currently, semitransparent films with rough surfaces mainly composed of polypropylene resin are being actively developed as films for medical, industrial, and food packaging applications.

Methods for producing such a translucent polypropylene film having a rough surface include a method of adding polyolefin to polypropylene in addition to polyethylene, a method of adding a blowing agent to polypropylene,
Alternatively, a method has been proposed in which a special nucleating agent such as a quinacridone derivative is added to polypropylene, which is then melt-molded to create a polypropylene sheet having a β-type crystal structure, which is then stretched.

These methods either have a narrow range of optimal conditions for obtaining the desired rough surface, require special molding conditions, have a low degree of surface roughening, or are inappropriately balanced with other physical properties. However, there are still some problems, and considerable improvements are needed.

As a result of intensive studies on polypropylene resin compositions suitable for producing translucent polypropylene films, the inventors of the present invention found that by combining a propylene-ethylene block copolymer and an organic peroxide, a scale expressing translucency was obtained. The present invention was achieved based on the discovery that a film with a certain level of haze has been significantly increased, the melt flow index can be easily controlled, and the haze level does not easily vary depending on molding conditions.

That is, the present invention is characterized in that: A: A block polymerization part having an ethylene content of 50 to 100% by weight, 0.5 to 60% by weight, and a propylene homopolymerization having a propylene content of 80% by weight or more, or a combination of propylene and other α-olefins. 100 parts by weight of a crystalline propylene-ethylene block copolymer consisting of 99.5 to 40% by weight of the copolymer and B: The decomposition temperature to obtain a half-life of 10 days is approximately 60°C.
The present invention relates to a polypropylene resin composition suitable for producing a translucent polypropylene film, comprising 0.001 to 1 part by weight of at least one of the above organic peroxides.

A: The crystalline propylene-ethylene block copolymer used in the present invention has a block polymerized portion having an ethylene content of 50 to 100% by weight.
The polymerization parts other than the block polymerization part are not particularly limited, but usually consist of a propylene homopolymerization part or a propylene-α-olefin* (*excluding propylene) copolymerization part with an average propylene content of 80% by weight or more. Examples of α-olefins include one or more selected from ethylene, butene-1, isobutene, hexene-1,4-methylpentene-1, styrene, and the like.

The proportion of block polymerized parts in A is 0.5 to
60% by weight, preferably 2 to 40% by weight, particularly preferably 3 to 30% by weight. If it is less than 0.5% by weight, the haze will be small and the haze increasing effect of the organic peroxide will be less likely to appear. 60% by weight
If it exceeds this, the haze level will be close to the upper limit, and the manufacturing cost of the block copolymer itself will be considerably high, so there will be little merit.

If the ethylene content in the block polymerization part of A is less than 50% by weight, the degree of haze will be low and the production of this block copolymer will be extremely difficult, making it difficult to carry out industrially and having little merit.

The organic peroxide used as component (B) in the present invention is suitably one having a decomposition temperature of 60°C or higher, preferably 60 to 150°C to obtain a half-life of 10 hours. Examples of such organic peroxides include lauroyl peroxide (62°C), benzoyl peroxide (72°C), cyclohexanone peroxide (97°C), t-butyl peroxyisopropyl carbonate (98°C), t-butyl peroxide Benzoate (105℃), methyl ethyl ketone peroxide (105℃), dicumyl peroxide (117℃), 2,5-dimethyl-2,5-
Di-(t-butylperoxy)hexane (118
℃), di-t-butyl peroxide (126℃),
Examples include 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane-3 (160°C).

The amount of component B used is based on 100 parts by weight of component A.
0.001 to 1 part by weight, preferably 0.005 to 0.5
Parts by weight, particularly preferably 0.01 to 0.2 parts by weight.

If the amount is less than 0.001 part by weight, no effect of the addition of organic peroxide will be observed. When the amount is more than 1 part by weight, the effect of addition is seen, but the melt flow index of the resulting polypropylene resin composition becomes too high, making it unsuitable for film production.

In order to improve the haze of the film made from the composition of the present invention consisting of component A and component B, or to improve the film forming suitability,
Adding the following C component is often effective.

Component C: polyethylene; copolymer of ethylene and α-olefin (a) and/or radically polymerizable polar unsaturated compound (b) [content of (a+b) in the copolymer is 50% by weight or less] ]
At least one of these.

Specifically speaking, component C includes high-density polyethylene, medium-density polyethylene, low-density polyethylene, ethylene and propylene, butene-1,
Copolymers with one or more selected from isobutene, hexene-1,4-methylpentene-1-, styrene, vinyl acetate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, etc. It is.

A suitable addition ratio of component C is 0.5 to 100 parts by weight, preferably 1 to 100 parts by weight, per 100 polymerized parts of component A.
The amount is 50 parts by weight, more preferably 2 to 30 parts by weight.

Various known additives may be optionally added to the composition of the present invention or to a composition obtained by adding component C to the composition of the present invention. What are known additives?
These include various stabilizers, antistatic agents, organic lubricants, antiblocking agents, and colorants.

The polypropylene resin composition of the present invention may be used for molding by mixing each raw material in advance and pelletizing it, or by simply feeding a mixture of each raw material directly to a molding machine. I don't mind.

The polypropylene resin composition of the present invention may be used as it is as an unstretched film, a uniaxially or biaxially oriented film, or it may be laminated onto another unoriented polyolefin film or a uniaxially or biaxially oriented polyolefin film. You may use it.

Note that a laminated film on an unstretched polyolefin film or a uniaxially stretched polyolefin film can be further stretched to form a uniaxially or biaxially stretched film. Thus, a single film or a laminate film using the polypropylene resin composition of the present invention may be used in an unstretched state or, if necessary, in a uniaxially or biaxially stretched state. A more beautiful and uniformly roughened surface can be obtained by uniaxially or biaxially stretching.

A translucent film made from the resin composition of the present invention, particularly a stretched translucent film, can be used in a wide range of applications as follows.

(1) By pasting this film onto printed materials, photographs, etc., the shiny appearance can be changed to a soft and calm appearance.

(2) When this film is printed, the finished print has a smooth and calm appearance.

(3) By laminating this film with metal foil such as aluminum, the glittering effect of the metal foil can be removed.

(4) When a metal such as aluminum is vapor-deposited on this film, a vapor-deposited film with no glitter can be created.

(5) This film has good impregnability with oils such as electrical insulating oil, so it is also excellent as an insulating layer for electrical equipment that requires oil impregnation (such as capacitors and transformers).

(6) Since this film has excellent mold release properties, it is used as a mold release film when molding unsaturated polyester resins, melamine resins, etc.

(7) Since this film can be heat-sealed, it can be used to make bags as is or to be placed in an automatic packaging machine. Furthermore, when heat is applied to the rough side, only that part becomes transparent, and this can be used to create a patterned film with a mixture of transparent and semi-transparent parts. This transparency can also be achieved by printing on the rough side with colorless ink.

(8) If an adhesive tape or adhesive sheet is made by applying an adhesive to one side of this film, the adhesive part will be inconspicuous even when attached to an article. Furthermore, even if you use this tape to repair a torn part of a document, etc. and copy it, the tape will hardly come out on the copying surface, resulting in clean copies.

As described above, the film made of the composition of the present invention has a very wide range of uses and is very useful. The present invention will be explained in more detail with reference to the following examples, but these examples are not intended to limit the present invention.

Example 1 A propylene-ethylene block copolymer with an ethylene content of about 30% by weight and a homopolymerized portion of propylene (melt measured according to condition L of ASTM D-1238-73). Mix 100 parts by weight of index 3.5g/10 minutes) and 0.1 parts by weight of benzoyl peroxide thoroughly in a mixer, and feed it to a pentizer.
It was melt processed into pellets at ℃. The melt index of this pellet was 7.3 g/10 minutes.
The obtained pellets were fed into an extruder and melt-extruded and laminated at 240°C onto a uniaxially stretched polypropylene film with a thickness of about 160 μm to a total thickness of 180 μm.
It was made into a two-layer sheet of m.

Next, the obtained sheet was set on a TMLong film stretcher, heated to 150°C, and stretched 7 times in the direction perpendicular to the stretching direction of the base material, uniaxially stretched polypropylene, to form a clean sheet with a thickness of 25 μm. A translucent film was obtained. In this film, the polypropylene base is biaxially stretched, and the layer of the composition of the present invention thereon is uniaxially stretched. The haze of this film was extremely high at 40% (the haze was measured using ASTM D1003-
61 methods were used to measure one piece of film).

Comparative Example 1 Example 1 without using benzoyl peroxide
Pellets were made in the same way. The melt index of the pellets obtained was 3.6 g/10 minutes, and the melt flowability was not improved.

In addition, a two-layer stretched film was made using this material in the same manner as in Example 1, but the haze was 22%.
It was inferior to Example 1.

Example 2 90 parts by weight of a propylene-ethylene block copolymer (melt index 4.5 g/10 min) with an ethylene content of 76% by weight, about 25% by weight of block copolymerized parts and the other homopolymerized parts of propylene. Pellets were prepared in the same manner as in Example 1 using 0.08 parts by weight of dicumyl peroxide and 10 parts by weight of low density polyethylene (melt index 5 g/10 minutes measured under condition E of ASTM D-1238-73). . The melt index of the pellets obtained (according to ASTM D-1238 condition L) was 7.8 g/10
It was hot in minutes.

Further, a film produced using this pellet in the same manner as in Example 1 had a haze level of 56%.

Comparative Example 2 Pellets were prepared in the same manner as in Example 2 without using dicumyl peroxide. The melt index of the pellets obtained was 4.7 g/10 minutes,
A film produced from this pellet in the same manner as in Example 2 had a haze of 28%, which was inferior to that in Example 2.

Example 3 The pellets used in Example 1 were fed into an extruder and melt-extruded at 250°C to produce a sheet with a thickness of about 1 m/m. After preheating this sheet to 130℃,
The film was stretched 5 times in the longitudinal direction by utilizing the difference in circumferential speed between two sets of nip rolls having different rotational speeds. This uniaxially stretched sheet is sent to a tenter,
The film was stretched 10 times in the width direction while being heated to 150°C, then heat treated at 150°C for 4 seconds, cooled, and wound up. The obtained film having a thickness of about 20 μm had a paper-like feel and a haze level of 75%.

Comparative Example 3 A two-layer laminated biaxially stretched film having a thickness of 25 μm was obtained in exactly the same manner as in Example 2 except that the benzoyl peroxide, which was the B component used in Example 2, was not added and only the A component was used. The haze of the film thus obtained was 9%, indicating that a satisfactory translucent film could not be obtained.

Comparative Example 4 The propylene-ethylene block copolymer of component A used in Example 2 was replaced with the following block copolymer, that is, the proportion of the block polymerized part in the whole was about 30% by weight, and this part contained ethylene. The polymerization rate is 45% by weight, the polymerization portion other than this block polymerization portion is a copolymer which is a homopolymerization portion of propylene, and the melt index is a block copolymer having a melt index of 4.5 g/10 minutes. Similarly, the thickness
A two-layer laminated biaxially stretched film of 25 μm was obtained.

The haze of the film thus obtained was 5%, indicating that a satisfactory translucent film could not be obtained.

Claims (1)

[Claims] 1 A: Block polymerization part with an ethylene content of 50 to 100% by weight, 0.5 to 60% by weight, and propylene homopolymerization part with a propylene content of 80% by weight or more, or a copolymerization part of propylene with other α-olefins, 99.5%. 100 parts by weight of a crystalline propylene-ethylene block copolymer consisting of ~40% by weight and B: 0.001 to 1 part by weight of an organic peroxide whose temperature is 60°C or higher to obtain a half-life of 10 hours. A polypropylene resin composition for producing a translucent polypropylene film.