JPH0691829A - Drawability protective film and production thereof - Google Patents

Abstract

PURPOSE:To obtain a surface protective film characterized by that a character or a pattern is drawn on the surface thereof by a pencil with hardness of about HB and having transparency of a degree capable of checking a defect. CONSTITUTION:A composite co-extrusion non-stretched film with total light transmissivity of 70% or more has an A-layer on one surface thereof and a B-layer on the other surface thereof and the A-layer consists of a specific polyolefin resin and 15-50 wt.% of inorg. particles of which the refractive index, aspect ratio and average particle size are specific and has Vickers hardness of 1.4-5.5 and surface roughness of 0.4-1.5mum and the B-layer is a selfadhesive layer with surface roughness of 0.03-0.18mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film which can be releasably adhered to the surface of a plate-like article such as a metal plate or a synthetic resin plate.

More specifically, the present invention relates to a protective film having a drawing property in which letters or patterns can be written with a pencil on the surface of a surface protective film attached to a plate-like article.

[0003]

2. Description of the Related Art Conventionally, in the case of a plate-like article such as a metal plate, a synthetic resin plate or a glass plate, in order to prevent dust from adhering to the surface of the article during the storage period before use or surface damage due to damage, Surface protective materials are used for the purpose of preventing damage in the processing steps such as bending or drawing after cutting these on-board articles into a certain shape.

As the surface protective material, there are known a paper-based protective paper and a film-based protective film. Protective paper is inexpensive and has the advantage that letters and patterns can be written on its surface, but once it is pasted, the inside base material cannot be seen, so there is a defect check after the sticking to the base material or the base material. There is a drawback that it is difficult to confirm the type. Compared to this, since the protective film based on the film has transparency, there is an advantage that the inner substrate can be seen well even after pasting with the substrate, but letters and patterns cannot be written with a pencil on the film Therefore, when cutting into a certain shape, it must be cut as a guide. Further, it has a drawback that the sample No. and the name cannot be written.

On the other hand, as a known example of the drawing property of an olefinic film, as seen in JP-A-53-31741, etc., a small amount of filler is added to an olefinic resin and then stretched in a uniaxial or biaxial direction. What you have done is known. However, for unstretched polyolefin films, surface protective films having good drawability and transparency are not known. This is because it was considered difficult to achieve these objects in view of the softness of the unstretched olefin resin and the opacity of the filler.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface protective film having a drawing property which eliminates the above drawbacks without losing the function of the surface protective film.

[0007]

The problems to be solved by the present invention are solved by the following means "1" to "5".

[1] An unstretched laminated polyolefin film having an A layer on one surface and a B layer on the other surface and a total light transmittance of 70% or more, wherein the A layer is an olefin resin and inorganic particles. Vickers hardness (H) and surface roughness (Ra) are 1.4 ≦ H ≦ 5.5, 0.4 μ ≦ Ra ≦ 1.5
and the B layer is an adhesive layer having a surface roughness (Ra) of 0.03 μ ≦ Ra ≦ 0.18 μ.

The aspect ratio of the "2" inorganic particles is 5 or less, the refractive index (D) and the average particle diameter (R) are 1.48≤D≤1.70, 2µ≤R≤10µ, and the addition amount is Is from 15 to 50% by weight, and the drawability protective film according to the above-mentioned item 1.

[3] The drawable protective film according to the above 1 or 2, wherein the layer A is mixed with 2 to 15% by weight of an olefin resin having a polar group.

[4] The drawing protective film according to any one of the above [1] to [3], wherein the A layer is mixed with a polystyrene resin and / or a polymethylmethacrylic resin in an amount of 2 to 15% by weight.

[5] Resin (A) mixed with inorganic particles
Layer) and adhesive resin (B layer) are respectively melted and then composite extruded onto a cooling drum and cast, wherein the castable film is the B-type protective film. A method for producing a drawable protective film, wherein the layer surface is on the drum side and the cooling drum temperature is 70 ° C. or lower.

In the present invention, the olefinic resin used in the layer A is medium density polyethylene, high density polyethylene, poly (4-methylpentene-1), polypropylene alone, or low density polyethylene, medium density polyethylene,
It is a mixture of two or more kinds selected from high-density polyethylene, poly-4-methylpentene-1, polypropylene, polystyrene, and polymethylmethacrylic resin. Further, a monomer copolymerizable with these resins may be copolymerized within a range not impairing the basic properties, or various additives may be blended.

The Vickers hardness (H) of the layer A of the present invention is 1.4≤H≤5.5, preferably 1.7≤H≤5.0. When the Vickers hardness of the layer A is less than 1.4, the drawability does not appear even if the inorganic particles are mixed. Also,
When the Vickers hardness is more than 5.5, the layer A becomes too hard, and therefore, when it is attached to a base material such as a synthetic resin plate or a metal plate, the adhesion between the layer B and the base material decreases due to the floating. The aspect ratio of the inorganic particles mixed in the layer A is 5 or less, preferably 3 or less, and the refractive index (D) is 1.48 ≦ D ≦ 1.7.
0, preferably 1.50 ≦ D ≦ 1.65, average particle diameter (R) is 2μ ≦ R ≦ 10μ, preferably 2.0μ ≦ R ≦
8 μ. Even if the inorganic particles having an aspect ratio of more than 5 are added, the drawing property is not expressed. If the inorganic particles having a refractive index of less than 1.48 or more than 1.70 are added, the transparency of the layer A is deteriorated. It becomes difficult to check the defect in the bonding with the base material and the defect check after the bonding. Further, even if the inorganic particles having an average particle size of less than 2 μm are added, the drawing property is not exhibited. If the inorganic particles having an average particle size of more than 10 μm are added, the surface roughness of the B layer surface becomes too large. It causes floating. It is presumed that this phenomenon is due to the fact that the surface roughness of the A layer affects the surface roughness of the B layer.

In the present invention, the surface roughness Ra of the layer A formed by adding the inorganic particles is 0.4 μ ≦ Ra ≦ 1.5 μ, preferably 0.45 μ ≦ Ra ≦ 1.4 μ. If the surface roughness of the A layer is less than 0.4 μ, the drawing property is not expressed,
If it exceeds 1.5 μm, the surface roughness of the B layer becomes too large. The surface roughness Ra of the B layer is 0.03 μ ≦ Ra ≦
0.18μ, preferably 0.04 ≦ Ra ≦ 0.16. It is practically difficult to reduce the surface roughness of the B layer to less than 0.03 μm, and if it exceeds 0.18 μm, floating occurs in bonding with the base material.

That is, it is advantageous to harden the layer A and increase the surface roughness thereof in order to make the surface protective film exhibit drawability. However, if the layer A is too hard,
If the surface roughness of the layer is too high, the surface roughness of the B layer will be too high, and the function as a protective film will be lost.

The inorganic compounds added to the layer A of the present invention include calcium carbonate, magnesium hydroxide, dolomite, silica, clay and the like. These inorganic particles have a constant shape and a constant refractive index. These shapes which are not flat favor the drawability, and the constant refractive index favors the transparency. However, even if these inorganic particles are used, the stretched film becomes opaque due to the generation of voids. By forming an unstretched film using these inorganic particles, a surface protective film having drawability and transparency can be obtained.

The adhesive layer resin composition used for the B layer, which is an adhesive layer, is an ethylene / vinyl acetate copolymer resin, an ethylene / acrylic acid copolymer resin, a styrene / isoprene / styrene copolymer resin, a styrene / butadiene resin. There are styrene copolymer resins and the like. You may add additives, such as a tackifier and a heat resistance agent, to these B layer resins as needed.

The olefin resin having a polar group mixed in the layer A is ethylene / acrylic acid copolymer resin, ethylene / methacrylic acid copolymer resin, ethylene / methyl acrylate copolymer resin, ethylene / ethyl acrylate. Examples thereof include copolymer resins, ethylene / vinyl acetate copolymer resins, and maleic acid-grafted polypropylene resins. The mixing amount of these polar group-containing olefin resins is 2 to 25% by weight, preferably 5 to 20% by weight. Mixing these resins has the effect of making the characters written on the layer A with a pencil easier to read. This is considered to be a phenomenon that occurs because the glossiness of the surface of the A layer is further reduced. If the mixing amount of these resins is less than 2% by weight, the effect is small, and if it exceeds 25%, expression of drawing properties or floating in bonding with a base material becomes a problem. Further, the polystyrene and polymethyl methacrylate resin mixed in the layer A are 2 to 15% by weight,
It is preferably 5 to 12% by weight. When these hard resins are appropriately dispersed in the surface layer, the pencil drawability becomes good. However, if the mixing amount is less than 2%, the effect is small, and if the mixing amount exceeds 15% by weight, floating occurs in bonding with the base material.

The total light transmittance of the composite film of the present invention is 7
It is 0% or more, preferably 75% or more. If the total light transmittance of the composite film is less than 70%, it becomes difficult to check the defects in bonding with the base material and check the defects of the base material.

As the composite coextrusion method in the present invention, a known composite extrusion method can be adopted. Further, in the composite extrusion, the film is layer B surface cast and the cooling drum temperature is 70 ° C. or lower, preferably 60 ° C. or lower. In the A-side layer casting, the casting is unstable, and at the same time, the surface roughness of the B layer becomes too large. The cooling drum temperature is 7
When the temperature exceeds 0 ° C, the adhesive force between the layer B and the drum becomes too strong, so that stable film formation cannot be performed.

The production of the drawable protective film by the composite coextrusion method can be carried out at a higher speed without worrying about the organic solvent, as compared with the method of coating by using the solvent.

The total thickness and the composition ratio of the two-layer film of A layer / B layer are not particularly limited, but the total thickness is in the range of 30 μ to 100 μ and the composition thickness is A / B. Is preferably in the range of 4/1 to 1/4.

Next, the method for producing the drawability protective film of the present invention will be explained, but the invention is not limited thereto. That is, the adhesive layer resin component which is the B layer and the A layer resin component are charged from separate charging ports by a melt coextrusion device,
The dies or short pipes are combined to form a complex fluid, which is then extruded. A two-layer composite unstretched film of layer B and layer A can be obtained by casting and winding so that the layer B surface of the molten film discharged from the die contacts the drum.

The drawable protective film of the present invention can be widely used as a protective film for various articles such as a synthetic resin plate or a metal plate, or for a protective film using its aesthetic appearance.

[0026]

The effects of the present invention are listed below. (1) The film obtained by the present invention has a drawability with a pencil and can check the defects of the substrate even after being bonded to the substrate. (2) Since the surface of the layer A is made uneven, it does not feel shiny and has an excellent aesthetic appearance. (3) Since it is produced by the coextrusion method, it is safer and cheaper than the method using a solvent.

[0027]

[Characteristics measurement method / evaluation criteria]

(1) Vickers hardness A Shimadzu microhardness meter type 2 manufactured by Shimadzu Corporation was used to
It was measured according to IS Standard B7734.

(2) Refractive Index of Inorganic Particles Liquids having different refractive indexes were put in a test tube, and inorganic particles were added thereto and shaken sufficiently, and the refractive index of the transparent liquid was shown.

(3) Aspect Ratio of Inorganic Particles Using a scanning electron microscope, the ratio of the major axis / minor axis of 10 particles was determined, and the average value was used as the aspect ratio.

(4) Average Particle Size of Inorganic Particles It was measured by a centrifugal sedimentation method using CAPA5000 manufactured by Horiba Ltd.

(5) Surface Roughness (Ra) Ra was measured according to JIS B0601 with a 0.25 mm cutoff.

(6) Total light transmittance (Tt) It was measured according to ASTM-D-1003-52.

(7) Floating A B-layer surface of a film consisting of two layers, A layer and B layer, was made to fit the resin plate, and pressure-bonded at room temperature (line pressure: 2 kg / 20 mm) with a small press roll. The adhesiveness (floating) between the film and the resin plate of the obtained laminate was visually determined. ◯: No floating between the resin plate and the film x: White floating due to floating between the resin plate and the film (8) Drawability From the top surface (layer A) of the film bonded to the resin plate Characters were written by a free hand using an HB pencil, and the drawability was visually evaluated. ◎: Characters that can be written on the surface of the A layer and the written characters are easy to read ○: Characters that can be written on the surface of the A layer ×: Characters that cannot be written on the surface of the A layer (9) Defect check Pre-painted resin plate with yellow magic Write a filled circle with a diameter of about 1 mm on the top, and attach the film to the surface in the same way as (7). Whether the defect check was possible or not was judged by visually observing from the film surface of the laminated plate. ○: Magic mark visible visually ×: Magic mark not visible visually

[0034]

【Example】

 Examples 1 to 6 and Comparative Examples 1 to 8 Next, the present invention will be described with reference to Examples.

Commercially available low-density polyethylene (melt index: 2 g / 10 min), high-density polyethylene (met index: 6 g / 10 min), polypropylene (melt index: 15 g / 10 min), polystyrene (melt index: 7.5 g / 10 min) Is pulverized with a crusher. Calcium carbonate, talc, mica, titanium oxide and clay having various particle sizes were mixed with these powder resins in the proportions shown in Table 1 and pelletized with a biaxial pelletizer to obtain a layer A resin composition.

These resins are supplied from the 40 mmφ side of a composite extruder (40 mmφ, 30 mmφ) having a T die.
On the other hand, from the 30 mmφ extruder side, an ethylene-vinyl acetate copolymer resin (Mitsui Polychemical Co., Ltd .: Evaflex P1)
405) is supplied. Extruder set temperature 200-220
The layer B was cast on a cooling drum having a surface temperature of 35 ° C. so that the layer B was in contact therewith and solidified to obtain a two-layer composite unstretched film having a thickness of 60 μ (A layer / B layer thickness ratio = 2/1).

The composite film thus obtained and a 1 mm thick polycarbonate resin plate (hereinafter referred to as a PC plate) were laminated at room temperature using a small roll laminator (linear pressure: 2 kg / 20 cm). evaluated.

As can be seen from Table 2, Examples 1 to 6 have P
The film was free from floating when it was attached to the C plate, had drawability on the surface of the A layer, and was capable of checking the defects of the PC plate even after it was attached to the PC plate.

Compared with this, low density polyethylene (LDP
Comparative Example 1 in which E) was used, Comparative Examples 3 and 4 in which talc having a large aspect ratio as inorganic particles and mica were used did not exhibit drawability. Also, polystyrene (PS) is
In Comparative Example 2 used for the layer, the single-layer film had drawability but could not be formed into a composite film with the B layer.

Comparative Example 5, in which titanium oxide was used as the inorganic particles, was opaque because it lacked drawability and could not be checked for defects.

Further, Comparative Example 6 in which the average particle diameter of calcium carbonate was 1.8 μ and Comparative Example 8 in which the added amount of calcium carbonate was 10% by weight did not exhibit drawing properties, and the average particle diameter was 11 μm. Comparative Example 7 using calcium carbonate has drawing properties, but floating occurred when it was attached to a PC board.

[0042]

[Table 1]

[0043]

[Table 2]

Examples 7 to 9 and Comparative Examples 9 to 10 The pelletizing raw material used in Example 1 was used in a composite extruder 4
It is supplied from 0 mmφ side and ethylene / vinyl acetate copolymer resin (Mitsui Polychemical Co., Ltd .: Evaflex P0803) / Scorets 5320 (Exxon Chemical Co., Ltd.) = 97/3 from the 30 mmφ side to make a two-layer composite. The membrane was made. The temperature of the cooling drum and the casting surface of the film (the surface in contact with the cooling drum) were measured under the conditions shown in Table 3, and
A composite unstretched film having a thickness (A layer / B layer = 1/2) was obtained. The obtained film was bonded to a 1 mm thick PMMA plate (polymethylmethacrylic plate) in the same manner as in Examples 1 to 6 and evaluated.

In Examples 7 to 9, the composite film was excellent in film-forming property, no floating occurred when it was attached to the resin plate, and it had drawability and could be checked for defects. In contrast, in Comparative Example 9 in which the cooling drum temperature was 80 ° C., the film B could not be wound because the layer B adhered to the cooling drum. Further, in Comparative Example 10 in which the layer A was cast so as to be in contact with the cooling drum, the film formation was unstable, and floating occurred even when it was attached to the resin plate.

[0046]

[Table 3]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B32B 27/20 Z 6122-4F // B29K 23:00 105: 16 B29L 9:00 4F (72) Inventor Yoichi Matsuura 1-5 Sakuramachi, Takatsuki City, Osaka Prefecture Toray Gosei Film Co., Ltd.

Claims (5)

[Claims] 1. A layer A on one surface and a layer B on the other surface,
An unstretched laminated polyolefin film having a total light transmittance of 70% or more, wherein the layer A is formed by mixing olefin resin with inorganic particles, and has Vickers hardness (H) and surface roughness (R).
a) is 1.4 ≦ H ≦ 5.5, 0.4 μ ≦ Ra ≦ 1.5
and the surface roughness (Ra) of the layer B is 0.03μ ≦ Ra ≦ 0.18μ, which is an adhesive layer. 2. The inorganic particles have an aspect ratio of 5 or less, a refractive index (D) and an average particle diameter (R) of 1.48 ≦ D ≦ 1.70, 2μ ≦ R ≦ 10μ, and the addition amount is The drawability protective film according to claim 1, wherein the drawability protective film is 15 to 50% by weight. 3. The drawing protective film according to claim 1 or 2, wherein the layer A is mixed with 2 to 25% by weight of an olefin resin having a polar group. 4. The drawable protective film according to claim 1, wherein the layer A contains a polystyrene resin and / or a polymethylmethacryl resin mixed in an amount of 2 to 15% by weight. 5. The resin (A layer) formed by mixing inorganic particles and the adhesive resin (B layer) are respectively melted, and then composite extruded onto a cooling drum and cast. A method of manufacturing the drawability protection film of
In the casting method, the B layer surface is on the drum surface side, and the cooling drum temperature is 70 ° C. or lower.