JP2010179625A - Non-extended resin film for surface protection and surface protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene resin film for surface protection and a protection film including the polypropylene resin film for surface protection and an adhesive layer laid on it; wherein the polypropylene resin film is suitable as a base film for the protection film which is excellent in dimensional stability and transparency, is low in foreign matters, has neither crease nor sagging in rolled form, excels in adhesive applicability or adhesion workability and is excellent in protection after adhesion treatment. <P>SOLUTION: A non-extended resin film for surface protection has thickness of 30 μm or more and 100 μm or less, wherein the film is obtained by extruding the molten resin in sheet form and heat treating under 70°C or more and less than melting point of the resin after cooling and solidifying it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface-protective polypropylene-based resin film and a surface protective film, and is excellent in processing suitability such as adhesive processing, has little additive migration and foreign matter, and is excellent in post-processing protection and transparency. In particular, the present invention relates to a surface-protective polypropylene resin film that is suitable for surface protection of various articles and a surface protection film using the surface-protective polypropylene resin film.

In order to prevent scratches, adhesion of dirt, contamination, etc. during processing of liquid crystal panels and polarizing plates of personal computers, word processors, electronic desk calculators, etc., a surface protection film made of synthetic resin with a removable surface protection film is used. It is practiced to attach to a polarizing plate for protection.
Polyethylene-based unstretched films have excellent tear resistance and are widely used (see, for example, Patent Documents 1 to 3).
However, since polypropylene-based unstretched film has good transparency and heat resistance, a surface protective film is applied to the surface of a metal plate, a decorative plate, a resin plate, a glass plate, etc. even in the surface protective film field. To prevent surface scratches, dirt, rust, etc. that tend to occur during mounting, transportation, processing, etc., and when processing and assembling electronic, precision products, parts and related materials such as liquid crystal panels and related materials such as polarizing plates It has been widely used as a paint film surface protection film to prevent scratches, dust adhesion, contamination, etc., and to protect the car body paint film from acid rain, dust, dust, etc. during transportation and storage of the car. (For example, see Patent Document 4)

The surface protective film is generally used by laminating an adhesive layer on the surface of a base film and fixing it to the surface of an object to be protected using the adhesive force of the adhesive layer.
In recent years, with the expansion of applications, demands for quality and cost reduction have become stronger, and there is a demand for a base film having excellent adhesive processability.
In particular, the processing temperature is increasing for the purpose of increasing the processing speed of adhesive processing, etc., and even when processed at a high temperature, thermal deformation due to the processing temperature is small, and dimensional stability during processing is good, There is a demand for dimensional stability at high temperatures (hereinafter, also simply referred to as heat-resistant dimensional stability) that suppresses the occurrence of hot flame during processing.

  Moreover, the polypropylene resin film which added the crystal nucleating agent for the purpose of improving the heat-resistant dimensional stability of a film is proposed (for example, refer patent document 5, 6).

  However, since the residence time during extrusion of the resin is relatively long in a large-scale apparatus at a production facility level considering economy, there is a minute foreign substance called fish eye due to aggregation and decomposition of the crystal nucleating agent in the film. There are problems that occur.

The minute foreign matter called “fish eye” is defined in, for example, Polymer Editing Committee, Polymer Dictionary, Taiseisha, 2000, Reprint 6th Edition, P337.
A fish eye refers to a small spherical shape or the like formed in a film product. The name was given because there are many things that have transparency like fish eyes. There are various types such as unmelted lumps resulting from insufficient kneading of the molding material, lumps due to gelation of a part of the raw material, lumps due to partial deterioration of the material during molding, and those with foreign matter as the core.

  In the case of a protective film for plating, if the fish eye is present, a protrusion is formed in the portion of the film where the fish eye is present, causing adhesion failure between the object to be protected by the protrusion and causing the adhesion layer and the object to be protected. Since a space is formed between them and the plating solution enters the space and the protective effect is reduced, it is necessary to reduce it as much as possible. In the case of a protective film for protecting the LCD panel, the fish eye on the surface of the protective film may be damaged by the unevenness or rubbing of the fish eye when pressed on the surface in contact with the LCD panel. That is a problem.

  Recently, liquid crystal plates have been inspected with a protective film for protecting the liquid crystal plate. If fish eyes are present, it may be determined that the liquid crystal plate itself is a defect. The development of films such as grades and low fish eye grades is required.

  In order to improve the heat-resistant dimensional stability, a composition in which an aromatic organophosphate metal salt is blended with a polypropylene resin having specific characteristics is extruded at a cooling roll temperature of 40 to 50 ° C. A polypropylene-based resin film that is excellent in workability and dimensional stability even in secondary processing such as film and metal vapor deposition and suitable for fiber packaging and food applications is disclosed (for example, see Patent Document 7).

  However, the above film has a problem in transparency because many spherulites with large crystal sizes are generated during cooling in addition to the fish eye and changes in physical properties.

  In addition, polypropylene-based unstretched films are handled in the form of rolls in processes such as actual production, storage, and adhesive application, but when anti-blocking agents and lubricants are used when forming such rolls, This improves slipperiness and anti-blocking property, makes wrinkles less likely to occur, and makes it easier to process adhesives. Alternatively, bonding to the adherend becomes easy (for example, see Patent Document 8).

  However, on the other hand, fish eyes and voids are generated as described above, and there is a problem that transparency is lowered, particles are dropped, and process contamination occurs.

  Therefore, the polymer part (component A) mainly composed of propylene is polymerized in an amount of 60 to 80% by weight of the total polymerization amount, and then in the second step, an ethylene-propylene copolymer having an ethylene content of 20 to 50% by weight in the gas phase. A block copolymer obtained by polymerizing 20 to 40% by weight of the polymerization part (component B), and the intrinsic viscosity ([η] B) of component B is 2.0 dl / g or more, B A block copolymer having a ratio ([η] B / [η] A) of an intrinsic viscosity ([η] B) of the component to an intrinsic viscosity ([η] A) of the component A of 1.8 or less is melt-kneaded. It has been proposed to improve the blocking resistance between films using a film made of a polypropylene block copolymer (see, for example, Patent Documents 9 and 10).

  However, there is a problem in transparency because the ethylene-propylene copolymer portion is dispersed in the film as an island component.

  A decorative sheet that does not substantially use a crystal nucleating agent, an antiblock, or a lubricant has been proposed (see, for example, Patent Document 11), but is intended for design properties and has a problem with transparency.

  With virtually no use of crystal nucleating agents, anti-blocks or lubricants, it is suitable for adhesive processing and adhesive processing, has little transferability of additives, and further provides protection and transparency of the adherend after processing. An excellent surface-protective polypropylene resin film has not been proposed so far.

Japanese Patent Laid-Open No. 10-309781 JP-A-11-165368 JP 2005-281328 A Japanese Patent Laid-Open No. 10-309781 JP 2001-213976 A JP 2002-146130 A JP-A-10-298367 JP 2003-213229 A JP-A-6-93061 JP 2007-27005 A JP 2003-39163 A

  The present invention is a surface protective film that is excellent in heat-resistant dimensional stability and transparency at the production level, has no wrinkles or sagging in a roll shape, has excellent adhesive coating properties and adhesive processability, and has excellent protective properties after adhesive processing. An object of the present invention is to provide a surface-protective polypropylene resin film suitable as a base film and a protective film in which an adhesive layer is provided on the surface-protective polypropylene resin film.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

  That is, the present invention is an unstretched resin film for surface protection having a thickness of 30 μm or more and 100 μm or less, the film extruding a molten resin into a sheet shape, cooling and solidifying, and at least 70 ° C., less than the melting point of the resin An unstretched film for surface protection, characterized by being heat-treated with

  In addition, the present invention is characterized by containing 50% by weight or more of a crystalline polypropylene resin having an isotactic pentad fraction (mmmm fraction) of 90% or more, and containing a crystal nucleating agent, an antiblocking agent or a lubricant. Is a non-stretched film for surface protection, characterized in that the pressure-sensitive adhesive layer is provided on at least one surface of the above-described surface-protective polypropylene resin film. .

Since the polypropylene resin film for surface protection of the present invention is excellent in heat-resistant dimensional stability, for example, it is suitable for secondary processing such as adhesive processing, and is particularly subjected to treatment such as drying at a high temperature around 130 ° C. In addition, since the occurrence of hot stagnation and film sagging is suppressed, the productivity of the secondary processing can be improved, and the generation of defective products due to hot sag and film sagging can be suppressed.
Moreover, since the polypropylene resin film of the present invention does not substantially contain an anti-blocking agent, the problem that the anti-blocking agent falls off can be avoided.
In addition, despite the fact that it contains substantially no lubricant or antiblocking agent, the surface roughness is appropriate, the film has excellent slipperiness and blocking resistance, and is excellent in rigidity. Is excellent.
Moreover, since it is excellent in transparency, it is excellent in the visibility of a to-be-protected body. In addition, despite its improved heat-resistant dimensional stability, it has excellent impact strength, has excellent adhesive coating properties and adhesive processability, and maintains good impact resistance. High reliability when used.
Therefore, it can be suitably used as a packaging for articles such as foods and precision parts, which are apt to be contaminated by films, and as a protective film for various precision parts.
Moreover, since the protective film of the present invention is based on the above-mentioned polypropylene resin film for surface protection, a protective film utilizing the characteristics of the above-mentioned base film can be obtained. It can be suitably used as a protective film in various precision products and parts that are strongly required to be suppressed and in the processing and assembly processes of the products and parts.

The unstretched resin film for surface protection of the present invention is obtained by extruding a molten resin into a sheet shape, rapidly cooling and solidifying, and then heat-treating at 70 ° C. or higher and lower than the melting point of the resin to increase the crystallinity. is there. Conventionally, as a means for increasing the degree of crystallinity, a method of adding a crystal nucleating agent and gradually cooling at a relatively high temperature when the molten resin is extruded and cooled and solidified has been taken. In the method, the spherulites became larger, and as the crystallinity increased, the film lost its flexibility and extensibility, and whitening occurred. On the other hand, the heat treatment (annealing treatment) employed in the present invention was flexible. It is possible to maintain elongation and transparency.
The surface protective film as used in the present invention is used for the purpose of protecting the surface of an article from adhesion of contaminants such as scratches, dust, fingerprints, water, and oil due to contact during assembly or transportation of the article. It is peeled off when the adherend is used.

  The unstretched film for surface protection of the present invention may be a single layer or a laminate. In the case of a single layer film, the film itself is required. In the case of a laminate, at least one of the layers constituting the film must be a layer whose crystallinity can be improved by annealing treatment. Hereinafter, the layers are collectively referred to as an annealable layer.

  As the resin constituting the annealable layer, a highly crystalline polypropylene resin having an isotactic pentad fraction (mmmm fraction) of at least 90% or more, more preferably 93% or more, and further preferably 95% or more is used. It is important to.

In addition, the said isotactic pentad fraction (mmmm fraction) comprises the said transparent resin layer by the ¹³ C-NMR (nuclear magnetic resonance) measuring method using the carbon C (nuclide) of mass number 13. It is calculated from the numerical value (electromagnetic wave absorption rate) obtained by resonating the resin composition at a predetermined resonance frequency, and defines the atomic arrangement, electronic structure, and molecular microstructure in the resin composition. The isotactic pentad fraction of polypropylene resin is the ratio of five propylene units determined by ¹³ C-NMR measurement and arranged in a predetermined arrangement, and is a measure of crystallinity or stereoregularity. It is used.

Homopolypropylene can be used when high rigidity exceeding 1100 MPa is required in Young's modulus. Even in the case of homopolypropylene, the upper limit of Young's modulus is about 1800 MPa.
On the other hand, when flexibility of 400 MPa to 1100 MPa is required, copolymerized polypropylene can be used within the range of the isotactic pentad fraction. Examples of the copolymerizable monomer include ethylene, butene, pentene and the like, and ethylene is preferable.
Copolymerization may be block or random. The proportion of copolymerization is preferably 85 mol% or more of propylene. Furthermore, in the case of random copolymerization, it is preferably 91 mol% or more, and in the case of block copolymerization, it is preferably 94 mol% or more. When the copolymerization is ethylene, a high effect by the annealing treatment can be obtained by making propylene within the above range.

The high crystalline polypropylene resin may include other resins such as a random-polymerized polypropylene resin and an ethylene-propylene copolymer rubber, for the purpose of, for example, improving the extrusion film forming property and improving the impact resistance. It is also possible to add an elastomer component such as a styrene-butadiene copolymer or a hydrogenated product thereof, an ethylene-propylene-diene monomer copolymer. It is also preferable to add an elastomer component particularly when flexibility is required.
However, if one with poor compatibility with the highly crystalline polypropylene resin is used, it will peel off at the interface between the resins during bending and cause whitening, cracks, breakage, etc. As a result, the excellent characteristics of the highly crystalline polypropylene resin are naturally reduced. Therefore, it is preferable that the amount of the various additives added is limited to 10% by weight or less, and the composition contains at least 90% by weight of the highly crystalline polypropylene resin.

  When flexibility is required, the Young's modulus is preferably 1000 MPa or less, more preferably 950 MPa or less, and particularly preferably 900 MPa or less. The Young's modulus can be appropriately adjusted not only by the above composition but also by annealing conditions described later.

The elongation at break of the unstretched film for surface protection of the present invention is preferably 200% or more, more preferably 250% or more, still more preferably 300% or more, and particularly preferably 350% or more. If it is less than 200%, it may be difficult to follow a curved adherend, or even a flat adherend may be easily broken when applied. The upper limit of the elongation at break is not particularly limited, but a practical range that can be used as a film for surface protection is preferably 1500% or less, and more preferably 1200% or less.
(Breaking elongation = (distance between chucks at break−distance between initial chucks) / distance between initial chucks × 100),

Factors required for the highly crystalline polypropylene resin to achieve the object of the present invention include the above-mentioned isotactic pentad fraction (mmmm fraction), melt flow rate (MFR) and molecular weight distribution ( MWD = Mw / Mn) is also important.
It is desirable to employ a highly crystalline polypropylene resin having a melt flow rate (MFR) in the range of 3 to 15 g / 10 min (230 ° C.) and a molecular weight distribution (MWD = Mw / Mn) of 2 to 4. On the other hand, if the melt flow rate is too large, the melt viscosity in the molding process is low, resulting in unstable shape maintenance, and whitening in the crystallization process and annealing process in the molding process. It may be difficult to obtain.

When the unstretched film for surface protection of the present invention is a laminate, at least one of the layers constituting the film and the layer constituting 30% or more of the thickness, and further at least two layers are annealable layers. It is preferable that The proportion of the annealable layer in the entire film is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 70% or more in terms of thickness.
Next, the reason why an excellent effect can be obtained by the annealing treatment employed in the present invention will be considered.

  In order to obtain the effect of the present invention, the crystal part of the resin constituting the annealable layer is composed of a monoclinic system generated by solid phase transition of a pseudo-hexagonal system part that is a metastable phase. It is considered that it is important that this monoclinic crystal is not a spherulite having a large crystal size but a crystal having a small crystal size. First, a pseudo hexagonal crystal structure and a monoclinic crystal will be described.

  The molecular chain in the pseudo hexagonal system has a united structure called nodules. Adjacent nodules have a structure that is easily displaced by stress, and they have a property that behaves like a liquid crystal (smectic liquid crystal) with respect to the stress, so that they can easily follow changes in external shape. The crystal is plastically deformed and can maintain transparency without causing breakage or whitening. Also, when impact stress is applied, the energy of impact is absorbed by the plastic deformation of the crystal. The impact resistance is also good. On the other hand, however, there is a problem that the size is easily changed by heating and aging.

  On the other hand, monoclinic crystals are packed with the molecular chains of polypropylene resin most closely, and have a crystal structure that is less likely to slip between adjacent lamellas. The change is small. However, on the other hand, it is difficult to follow the change in the outer shape, and in order to follow the change in the outer shape, fine peeling occurs at the interface between the crystals and the interface between the crystal part and the amorphous part, and they deviate from each other. It may be deformed depending on the situation. In particular, when many spherulites with large crystal sizes exist, when impact stress is applied, the impact energy cannot be sufficiently absorbed by the plastic deformation of the crystals, and There is a problem that whitening, cracks, breakage, and the like are likely to occur due to fine peeling at the interface between the crystal and the crystal part.

  In general, a polypropylene resin with low stereoregularity is easily crystallized in a monoclinic system under normal molding conditions, and it is difficult to produce a pseudo-hexagonal system part that is a metastable phase, Since the degree of crystallinity obtained is not so high, most of the crystal part is crystallized in a monoclinic system, and many spherulites with large crystal sizes are formed. In particular, when a crystal nucleating agent is added to increase the crystallinity, or when the molten resin is cooled and solidified at a relatively high temperature, it is mostly monoclinic and has a large crystal size. Spherulite.

  On the other hand, if it is rapidly cooled sufficiently, it will not become amorphous, but it cannot proceed completely to the monoclinic system, which is the stable phase, and the pseudo-hexagonal crystal, which is a metastable phase. Stay in the system.

In the present invention, without adding a nucleating agent to the highly crystalline polypropylene resin, first, it is molded and cooled and solidified at a relatively low temperature, so that the crystallizable part of the highly crystalline polypropylene is substantially a pseudo hexagonal part. A molded body consisting of only the above-mentioned material is heated (reheated) for a certain period of time at a certain temperature between the phase transition temperature (about 70 ° C.) and the melting point (about 160 ° C.) of the crystal part. By transforming a substantial part of the pseudo hexagonal crystal structure into the monoclinic system, the average particle size and amount of the formed spherulites and the pseudo hexagonal system and the monoclinic system Both ratios are considered to be precisely and independently controlled, enabling physical properties to be controlled.
In other words, by generating a quasi-hexagonal system part and generating a large amount of monoclinic phase by generating a quasi-hexagonal part without generating spherulites as much as possible during cooling and solidification, a certain amount of crystals with a small crystal size can be generated. It is estimated that
The crystal size is preferably 200 nm or less which does not scatter visible light. The amount of crystals (crystallinity) may be controlled depending on the intended use as described above, but it is estimated that the effect cannot be expected unless it is 20 wt% or more.

  In optimizing the size and amount of crystals in the polypropylene crystal part as described above, it is presumed that it is important to use a highly crystalline polypropylene resin having high stereoregularity as the polypropylene resin.

  Regarding the composition of the polypropylene resin, a polypropylene random copolymer resin having an α-olefin content of 5% by mass or less is preferable from the viewpoint of heat-resistant dimensional stability, if it is a homopolypropylene resin or a random copolymer polypropylene resin. .

The polypropylene resin film for surface protection of the present invention preferably has a film crystallinity of 30 to 65% according to the measurement method described later.
If the crystallinity is less than 30%, the heat-resistant dimensional stability is inferior, and it is not preferable because the film is liable to be flat when it is processed in a later step, resulting in poor flatness. On the other hand, when the crystallinity exceeds 65%, the transparency of the film is remarkably deteriorated. On the other hand, when the degree of crystallinity exceeds 65%, it is generally not practical because it contains a large amount of a crystal nucleating agent and requires a higher heat treatment temperature. The lower limit of the crystallinity of the film is more preferably 40% or more, and most preferably 50% or more from the viewpoint of heat-resistant dimensional stability. On the other hand, the upper limit of the crystallinity of the film is preferably 60% or less from the viewpoint of transparency.

In the surface-protective polypropylene resin film of the present invention, the crystal nucleating agent is preferably 50 ppm or less, and more preferably 10 ppm or less. The addition of an appropriate amount of crystal nucleating agent suppresses the generation of huge spherulites and can improve transparency. However, when the crystal nucleating agent is added in excess of 50 ppm, the molten resin is extruded into a sheet and cooled and solidified. Crystallization may proceed excessively, resulting in a decrease in transparency and an effect of annealing may not be obtained.
Further, although depending on the melt extrusion conditions of the resin, there is a case where fish eyes in the film tend to increase and become a problem. Further, it is not preferable because a problem such as a reduction in productivity such as pressure increase due to clogging of a filter provided in an extruder for the purpose of removing foreign substances in the resin occurs.

  Moreover, it is preferable that the content of antiblocking agents, such as inorganic and / or organic microparticles | fine-particles, in the film for surface protection polypropylene resin films of this invention is 50 ppm or less. The content of the anti-blocking agent is more preferably 10 ppm or less, and particularly preferably the detection limit or less by a usual quantitative method such as ash or elemental analysis. That is, it is preferable not to contain an antiblocking agent substantially. Here, substantially not containing an antiblocking agent has the same meaning as in the case of the above-mentioned lubricant. By this measure, the anti-blocking agent is prevented from falling off due to film abrasion in the film production and secondary processing steps, so that contamination, troubles, and the like due to the fall-off are suppressed.

  It is important that the polypropylene resin film for surface protection of the present invention has a content of a lubricant such as polyethylene wax, calcium stearate, erucamide, ethylenebiserucamide in the film of 50 ppm or less. The content of the lubricant is more preferably 10 ppm or less, and particularly preferably the detection limit or less by a usual quantitative method such as elemental analysis or extraction method. That is, it is preferable that substantially no lubricant is contained. Here, “substantially containing no lubricant” means forming a film without positively adding the lubricant. The above range is to include that there is a case where a minute amount is mixed due to brand switching or the like at the time of manufacturing a raw material polymer or film without positively adding a lubricant, and it is a preferable embodiment that substantially does not contain a lubricant. is there. In the method of blending the lubricant and improving the slipperiness of the film due to the countermeasure, the migration of the lubricant to the film surface and the contamination of the packaged object or the protected object due to the subsequent transfer to the packaged object or the protected object occur. It is blocked and the clarity of the article to be packaged and the object to be protected is maintained.

  It is preferable to add an antioxidant such as an acrylate-based antioxidant, a phosphorus-based antioxidant, and a phenol-based antioxidant to the polypropylene resin film for surface protection of the present invention.

  The acrylate antioxidant of the present invention is an antioxidant having a phenol derivative containing an acrylate residue in the molecule. Examples of the acrylate compound include 2,4-di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate, 2,4-di-t. -Amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) butyl] phenyl acrylate, and the like.

  As said acrylate compound, it can select from a commercially available thing suitably and can be used. For example, Sumitizer GM (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., which is 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4 -Sumitizer GS (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., which is di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate Can do. In particular, it is preferable to use a Sumilizer GS (registered trademark).

Although the compounding quantity of the said acrylate antioxidant in this invention is not limited, The range of 100-1000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 200 to 800 ppm is more preferable, and 300 to 700 ppm is more preferable. When it exceeds 1000 ppm, the contamination of the cooling roll increases in the film forming step, which is not preferable. The film is also unfavorable because it dyes a pale yellow color unique to antioxidants. On the contrary, if it is less than 100 ppm, the combined effect described later is decreased, which is not preferable. It is preferable to lower the upper limit of the blending amount of the acrylate antioxidant alone than the above two kinds of antioxidants. The acrylate antioxidant is a polypropylene resin rubber compared to other antioxidants. Due to the high solubility in the component, it is more distributed to the rubber component in the film, and the rubber component portion has a slower crystallization rate by the cooling roll than the base resin, so that the rubber is in contact with the cooling roll. It is surmised that the above-mentioned acrylate antioxidant distributed to the components easily migrates to the cooling roll, and thus is caused by increasing the contamination degree of the cooling roll.
For example, this is a unique phenomenon that occurs in the present invention that does not occur in the film formation using the homopolypropylene resin disclosed in Patent Document 23 and the like described above.

  Specific examples of the phosphorus-based antioxidant used in the present invention include, for example, a heat stabilizer that contains a trivalent phosphorus atom in the molecule, and the phosphorus atom has at least one P—O—C bond. It is done. Examples thereof include tributyl phosphite and trioctyl phosphite.

  Commercially available products can also be used as the phosphorus-based antioxidant used in the present invention. For example, Irgafos 168 (manufactured by Ciba Specialty Chemicals), Irgafos 38 (manufactured by Ciba Specialty Chemicals), GSY- P101 (manufactured by Yoshitomi Fine Chemicals), Ultranox 641 (manufactured by GE Specialty Chemicals), and the like.

  Although the compounding quantity of the said phosphorus antioxidant in this invention is not limited, The range of 500-5000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 1000 to 4000 ppm is more preferable, and 1500 to 3000 ppm is more preferable. If it is less than 500 ppm, the effect of using an antioxidant described later decreases, which is not preferable. On the other hand, if it exceeds 5000 ppm, the effect of using an antioxidant described later is saturated, causing film whitening due to the migration of the antioxidant to the film surface, contamination of the cooling roll in the film forming process, and the like. It is not preferable.

  The phenolic antioxidant used in the present invention is an antioxidant having a phenol derivative in the molecule, such as 2,6-di-t-butyl-4-methylphenol, 2,6-di-t. -Butyl-4-ethylphenol and the like.

  Commercially available products may be used as the phenolic antioxidant used in the present invention, for example, Irganox 1010 (Ciba Specialty Chemicals), Irganox 1076 (Ciba Specialty Chemicals), Irganox 1330 (manufactured by Ciba Specialty Chemicals), Irganox 3114 (manufactured by Ciba Specialty Chemicals), Irganox 1425WL (manufactured by Ciba Specialty Chemicals) and the like.

  Although the compounding quantity of the said phenolic antioxidant in this invention is not limited, The range of 500-5000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 1000 to 4000 ppm is more preferable, and 1500 to 3000 ppm is more preferable. If it is less than 500 ppm, the effect of using an antioxidant described later decreases, which is not preferable. On the other hand, if it exceeds 5000 ppm, the effect of using an antioxidant described later is saturated, causing film whitening due to the migration of the antioxidant to the film surface, contamination of the cooling roll in the film forming process, and the like. It is not preferable.

  In the present invention, as described above, it comprises at least two antioxidants selected from at least one selected from the group consisting of acrylate antioxidants, phosphorus antioxidants and phenolic antioxidants. However, it is a more preferable embodiment that three types of acrylate antioxidant, phosphorus antioxidant and phenolic antioxidant are used in combination.

  The above three kinds of antioxidants are not limited to one type each. Two or more of each type may be used in combination, and in addition to the above three types of antioxidants, for example, an antioxidant having another structure such as a sulfur-based antioxidant may be further used in combination.

  By using a plurality of the above-mentioned antioxidants in combination, a high level of fisheye mixing suppression effect that cannot be obtained by a combination of conventionally known antioxidants is expected.

In the present invention, the polypropylene resin film for surface protection of the present invention preferably has 0 fisheye / m ² having a maximum diameter of 0.2 mm or more in the film. Further, the number of fish eyes having a maximum diameter of 0.1 mm or less is preferably 100 / m ² or less. The number of fish eyes having a maximum diameter of 0.1 mm or less is most preferably 0 / m ² or less, but the above range is preferable in view of economic efficiency and market demand. 2-80 pieces / m ² or less is more preferable, and 2-60 pieces / m ² or less is more preferable. By this correspondence, when it is used as a base film of a protective film, for example, when it is used as a base film of a protective film, it is possible to suppress the occurrence of troubles due to the penetration of the plating solution into the protective part due to the above-mentioned poor adhesion.

  Moreover, the polypropylene resin film for surface protection of the present invention has a thickness variation rate of ± 1 to 10%. When the thickness variation rate is less than 1%, there is no problem in terms of quality, but the time required for adjusting the thickness becomes enormous and the economic efficiency is remarkably lowered, which is not realistic. On the other hand, when the thickness variation rate exceeds 10%, the heat-resistant dimensional stability and transparency vary in proportion to the thickness variation, and the flatness of the film (waving and curling) is deteriorated, which is not preferable. The thickness variation rate is more preferably ± 1.5 to 8%, and most preferably ± 2 to 5%.

[Control of crystallinity in cooling condition control]
The extruded film of the present invention is an unstretched film formed by a T-die method, and the thickness of the film is 30 to 100 μm. Furthermore, 80 micrometers or less are preferable. If it is less than 30 μm, the protective film may be inferior in handleability or may be torn when the adherend comes into contact with another. If it exceeds 100 μm, the followability to the adherend may be inferior.
Film forming conditions for using the polypropylene resin composition of the present invention as an extruded film are preferably performed at a die temperature of 200 ° C. to 250 ° C. and a cooling roll temperature of 30 ° C. or less, and more preferably 25 ° C. or less. When the chill roll temperature exceeds 30 ° C., it is not preferable because a pseudo hexagonal system part is hardly generated.
Moreover, although it does not specifically limit about cooling time, The range of 1.0 second or more is preferable. When the cooling time is less than 1.0 second, the cooling effect is insufficient, and thus it is not preferable because a pseudo hexagonal system part is hardly generated. On the other hand, the upper limit of the cooling time is not particularly limited from the viewpoint of the crystallinity of the film, but is preferably 5 seconds or less from the viewpoint of economy and productivity.

[Control of crystallinity in annealing condition control]
The film thus cooled is again subjected to heat treatment (annealing treatment). The heat treatment may be performed by winding the cooling film once in a roll and then unwinding it again. However, the heat treatment is preferably performed in a series of film production steps without winding after film formation. By being carried out in a series of manufacturing processes, when wound into a roll, it is heat-treated and becomes a film with improved elastic modulus, dimensional stability, slipperiness and blocking resistance, which are the effects of the present invention. As a result, it is difficult for troubles such as samurai and sagging at the winding festival to occur.
Examples of the heating process in the actual film manufacturing process include heating with a heating roll, heating with hot air or heated steam, heating with an infrared heater, etc., but the temperature can be quickly raised, and precise temperature control is required. The method of passing through a heating roll is the most preferable because it is possible. If the temperature of the film does not rise quickly to an appropriate temperature, the haze of the film may increase. If precise temperature control cannot be performed, unevenness of film characteristics such as haze unevenness may occur.

As a specific example, it is performed by contacting with at least one heating roll. Moreover, it is also mentioned as a preferable example that a film is passed between two heating rolls and one surface is sequentially heated with each heating roll. The crystallinity can be controlled by the heating temperature.
In addition, it was confirmed that the heating time was effective by heating for 1 second or more. The adjustment of the heating time is performed by adjusting the contact time with the heating roll, and can be controlled by the traveling speed of the film, the diameter of the heating roll, and the holding angle of the film on the roll. In order to further increase the heating time, it is possible to use three or more heating rolls. The upper limit of the heating time is not particularly limited as long as there is no problem with a series of film production facilities, but there is no difference in the effect even if the treatment is performed for more than 1 to several seconds where the phase transition is considered to be completed. From the viewpoint of productivity and economic constraints of the apparatus, 30 seconds or less is preferable, 10 seconds or less, and particularly 5 seconds or less are preferable. If the heating rolls are held unnecessarily long, surface roughness such as scratches or heating rolls may occur.
The lower limit of the heating temperature is preferably 70 ° C. or higher, more preferably 80 ° C. or higher, which is the temperature at which the pseudo-hexagonal polypropylene transitions to a monoclinic crystal. If it is less than 70 degreeC, a solid phase transition will not generate | occur | produce and the effect of this invention will not be acquired.
The upper limit of the heating temperature needs to be less than the melting point of the resin constituting the outermost layer of the film. The melting point of polypropylene resin, which is generally handled industrially, is 140 ° C to 160 ° C.
The upper limit of the heating temperature is preferably 140 ° C. or lower.
Further, the temperature at which the solid phase transition from pseudo hexagonal crystal to monoclinic crystal of polypropylene is from 80 ° C. to 120 ° C., so the upper limit temperature of heating is more preferably 120 ° C. or less.

When heating with a roll of film, adhesion failure due to heat shrinkage of the film may occur. In that case, it is preferable to use a nip roll or a suction roll.
However, since the heated film is soft and there is a concern about transfer to a film having a surface shape of not only a heating roll but also a nip roll and a suction roll, selection and management of the roll material and surface roughness are important. When a nip roll is used, the film is strongly pressed by the roll, and therefore both surfaces of the annealing roll and the nip roll are preferably flat like a mirror surface. When the nip roll is not used, the mirror surface as described above may be used, but it is also preferable to use a satin finish for the purpose of sliding the anneal roll surface and the film surface.

  The extruded film of the present invention can be subjected to surface treatment such as corona discharge treatment or flame treatment by a method generally employed industrially.

In this invention, it is preferable that it is a surface protection film which provides an adhesive layer in at least one surface of the above-mentioned surface protection polypropylene-type resin film. By the correspondence, the characteristics of the polypropylene resin film of the present invention described above can be effectively utilized, and the applicability in a wide field as a protective film is improved.
In particular, for example, applications that prevent scratches, adhesion of dirt, contamination, etc. during the processing and assembly of electronic and precision products such as liquid crystal panels and polarizing plates, precision products, parts and related members, and connection of flexible printed circuit boards As a method of partially plating the terminal part, etc., a mask is formed by sticking an adhesive film to the non-plated part and then plating, or a resist film or etching resistance provided on the non-etched surface in the etching process when manufacturing the shadow mask It can be suitably used as a protective film in plating and etching processes such as a method for protecting a film.
Further, the polypropylene resin film of the present invention is excellent in heat-resistant dimensional stability, and in the above-mentioned adhesive processing, for example, even if the drying temperature in the drying process is increased, the occurrence of hot stagnation and film sagging is suppressed. It becomes possible to increase the productivity of adhesive processing. Moreover, generation | occurrence | production suppression of the inferior goods resulting from a hot bath or film sagging can be suppressed.

  The kind, thickness, adhesive strength, and the like of the pressure-sensitive adhesive layer are not limited. What is necessary is just to select suitably by market demand. Moreover, the lamination method of this adhesive layer is not limited. The coating method and the extrusion laminating method may be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

  The measurement and evaluation methods employed in this specification are as follows.

1. Melt flow rate [MFR]
According to JIS K7210, the method of Condition-14 (load 2.16 kg, temperature 230 ° C.
Measured with

2. Ethylene content The ethylene content was measured by ¹³ C-NMR method according to the method described on page 616 of Polymer Handbook (published by Kinokuniya, 1995).

3. Haze value Measured according to JIS-K-6714 using “Haze Tester J” manufactured by Toyo Seiki Seisakusho.

4). Film crystallinity Measured using wide-angle X-ray diffraction transmission method (RIGAKU RINT2500).

8). Young's modulus / breaking elongation In accordance with JIS K7127, the sample shape conforms to the No. 1 type test piece (sample length 200 mm, sample width 15 mm, chuck distance 100 mm), and crosshead speed 200 mm / min. The MD direction (film longitudinal direction) was measured at 23 ° C. Values were averaged over 5 samples.

9. Fisheye The molded film was cut 33.3 cm in the flow direction × 30 cm in the direction transverse to the flow direction, placed on a plate irradiated with a fluorescent lamp from below the film, and visually observed with transmitted light. Measure fish eyes of 1 mm or more. Next, if the counted fish eye is immersed in liquid nitrogen and hardened, it is cut in half with a razor and the cross section of the fish eye is observed with a microscope at 50 to 300 times. For example, if there is no foreign matter such as cellulose, it is an unmelted lump, a lump due to gelation of a part of the raw material, or a gel-induced fish such as lump due to partial deterioration of the material during molding. Judged as eye. If there is a nucleus, it is judged as a fish eye caused by a foreign object and excluded from the count.

10. Film density Measured using a density gradient tube method.
The density gradient liquid is prepared using isopropyl alcohol and distilled water, and is managed in a thermostatic bath. The temperature of the thermostatic bath was 30 ± 0.1 ° C., and the immersion time of the sample was 16 ± 8 hours.

11. Isotactic Pendat fraction
^The propylene monomer at the center of a chain meso-bonded with five consecutive propylene units, showing the proportion of isotactic chains in pentad units in the polypropylene molecular chain measured using ¹³ C-NMR (Mmmm). Specifically, it is a value determined as the mmmm peak fraction in the total absorption peak in the methyl carbon region in the ¹³ C-NMR spectrum.

12 Roll wrinkle and sagging The presence or absence of wrinkles on the surface of the product roll was visually confirmed. Further, it was confirmed with a finger that there was no difference in winding hardness partially in the width direction. Evaluation was performed immediately after winding and after 3 days.

13. Adhesive Application Acrylic adhesive (viscosity 30 × 10 ⁻³ Pa · s) was applied by hand coating with a Meyer bar. The presence or absence of repelling of the adhesive was confirmed visually.

14 Contamination After the tape was applied to the surface of the sample film, it was stored at 40 ° C. × 92% RH for 1 week and then peeled off. The adhesive surface of the tape was visually observed to confirm the presence or absence of dirt.

15. Scratch resistance Rubing was performed with a brush (hardness 2B) at a constant load, and the degree of scratching was visually confirmed.

16. Thermal deformation resistance JIS Z1715 was cited. That is, the film is cut into a rectangle of 20 mm × 250 mm, marked with a distance of 150 mm, heat-treated for 30 minutes in a hot air dryer at 80 ° C. under no load, and then the vertical and horizontal dimensions of the film. Was measured, and the thermal shrinkage rate was determined according to the following formula.
Thermal deformation rate = {(distance between gauge points before heating−distance between gauge points after heating) / distance between gauge points before heating} × 100 (%)
If both the flow direction and the width direction were less than 1%, it was judged good.

Example 1
100% by weight of polypropylene homopolymer resin (FLX80E4 manufactured by Sumitomo Chemical Co., Ltd., MFR = 7 isotactic pendant fraction 90% or more) is melt-extruded by a T-die film forming machine and cooled at a cooling roll temperature of 25 ° C. Time 2.4 seconds (film forming speed 40 m / min), draft ratio at the time of taking molten resin 0.64 (die slip gap: 0.5 mm, die slip outlet molten resin speed: 4.8 m / min, air gap : 8 cm), an unstretched film having a thickness of 40 μm was obtained. Thereafter, the unstretched film is heated to 120 ° C. by passing through a heating roll. The warming time was 3.0 seconds. The resin temperatures in the supply zone, kneading zone and metering zone of the extruder were set to 230, 240 and 235 ° C, respectively.
The results are shown in Table 1.
The polypropylene-based resin film obtained in this example was good in all properties shown in Table 1 and high in quality.

(Example 2)
A polypropylene resin film of Example 2 was obtained in the same manner as in Example 1 except that the cast cooling time was 1.2 seconds and the heating roll passage time was 1.5 seconds. The results are shown in Table 1.
The polypropylene resin film obtained in this example had the same properties as the polypropylene resin film obtained in Example 1 and was of high quality.

(Example 3)
A polypropylene resin film of Example 3 was obtained in the same manner as in Example 1 except that the film thickness was 80 μm. The results are shown in Table 1.
The polypropylene resin film obtained in this example had the same properties as the polypropylene resin film obtained in Example 1 and was of high quality.

Example 4
A polypropylene resin film of Example 4 was obtained in the same manner as in Example 1 except that the heating roll temperature was 100 ° C. The results are shown in Table 1.
The polypropylene resin film obtained in this example had the same properties as the polypropylene resin film obtained in Example 1 and was of high quality.

(Example 5)
The same method as in Example 1 except that the resin type was a polypropylene resin containing ethylene component (WF836DG3, Sumitomo Chemical Co., Ltd. MFR = 7, ethylene component 0.6 mol%, isotactic pendant fraction 90% or more). A polypropylene resin film of Example 5 was obtained. The results are shown in Table 1.
The polypropylene resin film obtained in this example had the same properties as the polypropylene resin film obtained in Example 1 and was of high quality.

(Example 6)
A polypropylene resin film of Example 6 was obtained in the same manner as in Example 1 except that the resin type was polypropylene-ethylene block copolymer resin (KS23F8, MFR = 3, manufactured by Sumitomo Chemical Co., Ltd.). The results are shown in Table 1.
The polypropylene resin film obtained in this example is not highly transparent in terms of the characteristics of the resin compared to the polypropylene resin film obtained in Example 1, but has the same mechanical properties. It was high quality.

(Example 7)
In the method of Example 1, a polypropylene resin film of Comparative Example 3 was obtained in the same manner as in Example 1 except that 5 parts by weight of the master batch resin (M-1) containing a crystal nucleating agent was added. The results are shown in Table 2.
In the polypropylene resin film obtained in this comparative example, the fish eye significantly increased as compared with the polypropylene resin film obtained in Example 1.

(Comparative Example 1)
In the method of Example 1, the polypropylene resin film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the heating roll temperature was changed to 50 ° C. The results are shown in Table 2.
Although the polypropylene resin film obtained in this comparative example was excellent in transparency, the crystallinity of the film was lowered and the heat resistant dimensional stability was poor.

(Comparative Example 2)
In the method of Example 1, a polypropylene resin film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the cooling roll temperature was changed to 80 ° C. The results are shown in Table 2.
The polypropylene-based resin film obtained in this comparative example was of low quality because its crystallization progressed and transparency was lowered. In addition, due to insufficient solidification, film quality deteriorates, such as touch roll marks.

(Comparative Example 3)
In the method of Example 6, the polypropylene resin film of Comparative Example 3 was obtained in the same manner as in Example 6 except that the heating roll temperature was changed to 50 ° C. The results are shown in Table 2.
The polypropylene-based resin film obtained in this comparative example was inferior in transparency, and had a low quality inferior in heat-resistant dimensional stability because the crystallinity of the film was lowered.

(Comparative Example 4)
In the method of Example 6, the polypropylene resin film of Comparative Example 4 was obtained in the same manner as in Example 6 except that the cooling roll temperature was changed to 80 ° C. The results are shown in Table 2.
The polypropylene-based resin film obtained in this comparative example was of low quality because its crystallization progressed and transparency was lowered. Further, due to insufficient solidification, touch roll marks are generated or the flatness of the film itself is impaired, resulting in a decrease in film quality.

The unstretched film for surface protection of the present invention is characterized by high crystallinity, good rigidity and heat resistance, and excellent transparency.
Because it is excellent in rigidity and heat-resistant dimensional stability, for example, it is excellent in secondary processing such as adhesive processing, and even when processing such as drying at high temperatures, the occurrence of hot scum and film sagging is suppressed. Therefore, it is possible to improve the productivity of the secondary processing and to suppress generation of defective products due to hot metal or film sagging.

Further, depending on the method for inspecting the adherend, it may be necessary to achieve both high transparency and rigidity, but this can be achieved because the unstretched film for surface protection of the present invention does not have a large spherulite structure.
Moreover, since the polypropylene resin film of the present invention does not substantially contain an anti-blocking agent, contamination due to falling off, occurrence of trouble, and the like are suppressed.
In addition, since the polypropylene resin film of the present invention does not substantially contain a lubricant, for example, when used as a base film for a packaging bag or a protective film, there is no transfer of the lubricant to the protected body, so that the protection is achieved. Contamination of the body is suppressed.
Moreover, although the lubricant and the antiblocking agent are not substantially contained, the slipperiness of the film is good and the rigidity is excellent, so that the handleability of the film is excellent.
In addition, although it has a high degree of crystallinity and excellent rigidity, it has an appropriate transparency, so that the visibility of the protected object is excellent.
Moreover, since the protective film of the present invention is based on the polypropylene resin film, a protective film utilizing the characteristics of the base film can be obtained. It can be suitably used as a protective film in various kinds of strong precision products and parts and the processing and assembly processes of the products and parts.
Therefore, it is important to contribute to the industry.

Claims (4)

  An unstretched resin film for surface protection having a thickness of 30 μm or more and 100 μm or less, and the film was heat-treated at a temperature of 70 ° C. or higher and lower than the melting point of the resin after the molten resin was extruded into a sheet and cooled and solidified. An unstretched film for surface protection characterized by being a thing.   An unstretched film for surface protection comprising 50% by weight or more of a crystalline polypropylene resin having an isotactic pentad fraction (mmmm fraction) of 90% or more.   An unstretched film for surface protection, wherein the content of a crystal nucleating agent, an antiblocking agent or a lubricant is 50 ppm or less.   A surface protective film comprising a pressure-sensitive adhesive layer on at least one surface of the surface-protective polypropylene resin film according to claim 1.