JPH08134415A - Surface protective film - Google Patents

Abstract

PURPOSE: To provide a surface protective film which can be suitably used for preventing a metal plate, a resin plate, etc., from being marred or contaminated during drawing and is excellent in workability in drawing. CONSTITUTION: This film is obtained by forming a pressure-sensitive adhesive layer at least on one side of a film base comprising a propylene/α-olefin block copolymer (BPP), wherein the propylene/α-olefin copolymer rubber (OPR) particles dispersed in a polypropylene matrix phase have an area-mean particle diameter of at most 1.5μm and a number-mean particle diameter of at most 1.0μm and wherein the film base satisfies the relation of the formula 0.1 <= 9146/28}(A×B)/T]/C}×D<=280 [wherein A and B respectively are tear strengths (kg/cm) in the machine and transverse directions; T is the OPR content (wt.%) of the BPP; C is the thickness (μm) of film; and D is the α-olefin content (wt.%) of the OPR].

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 having excellent drawability, which is preferably used for preventing scratches or stains during drawing of metal plates, resin plates and the like.

[0002]

2. Description of the Related Art Stainless steel plates, aluminum plates, steel plates,
For the purpose of surface protection of metal plates such as copper plates or coated steel plates coated with these (hereinafter collectively referred to as "metal plates"), or to prevent scratches and stains that occur when drawing metal plates. A surface protection film is used. Conventionally, vinyl chloride resin has been mainly used as a surface protective film, but since it contains chlorine, toxic gas at the time of waste treatment has become a problem. For the purpose of solving this, a method using a polyolefin resin has been proposed. For example, a polyolefin having specific physical properties (Japanese Patent Laid-Open No.
-21239), polyolefin multilayer film (JP
56-55252), a polyolefin-based composition (JP-A-4-
No. 106175) and ethylene propylene elastomer (JP-A-6-220412).

[0003]

However, since none of the films obtained by the above method stretches uniformly during drawing, there is a problem that the constriction pattern generated in the resin adheres to the metal plate or the film tears. It was still insufficient. The present invention has been made in view of such circumstances, and an object thereof is to provide a surface protection film having excellent drawability.

[0004]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have found that propylene having a specific dispersed particle diameter
It was found that the above object can be achieved by the α-olefin block copolymer, and the present invention has been completed based on this finding. That is, the present invention provides a surface protective film obtained by forming a pressure-sensitive adhesive layer on at least one surface of a film substrate made of a propylene-α-olefin block copolymer having the following physical properties (1) and (2). Is. (1) The area average particle size of the propylene-α-olefin copolymer rubber particles dispersed in the polypropylene matrix phase is 1.5 μm or less, and the number average particle size is 1.0 μm.
m or less (2) The film substrate is in the range represented by the following formula: 0.1 ≦ {[(A × B) / T] / C} × D ≦ 280 (In the formula, A is the tear strength in the M direction. (Kg / cm), B is T
Direction tear strength (kg / cm), T is propylene-α-
Content of propylene-α-olefin copolymer rubber in olefin block copolymer (wt%), C is film thickness (μm) and D is content of α-olefin in propylene-α-olefin copolymer rubber Amount (% by weight)

The present invention will be specifically described below. The propylene-α-olefin block copolymer (hereinafter referred to as “BPP”) in the present invention is a polypropylene block and a copolymer rubber block of propylene and an α-olefin having 2 to 12 carbon atoms (excluding 3). Is a block copolymer consisting of As the α-olefin,
Ethylene, 1-butene, 3-methyl-1-butene, 3-
Methyl-1-pentene, 4-methyl-1-pentene, 4
-Dimethyl-1-pentene, vinylcyclopentane, vinylcyclohexane and the like. These α-olefins may be used alone or in combination of two or more.

[0006] BPP used in the present invention, (1) an area average particle diameter of the propylene -α- olefin copolymer rubber particles dispersed in a polypropylene matrix phase (hereinafter "D _S"
Is 1.5 μm or less and the number average particle size (hereinafter referred to as “D _N ”) is 1.0 μm or less, and D _S is preferably 1.0 μm, particularly 0.8.
μm is preferred. If D _S exceeds 1.5 μm, breakage occurs during drawing, which is not preferable. Further, D _N is preferably 0.8 μm, and particularly preferably 0.5 μm.
When D _N exceeds 1.0 μm, breakage occurs during drawing, which is not preferable.

Regarding the distribution of D _N, the maximum particle size is 0.6
It is preferably μm or less and has a standard deviation of 1.5 or less. Further, in the film of the present invention, the film base material (2) needs to be in the range represented by the following formula. 0.1 ≦ {[(A × B) / T] / C} × D ≦ 280 (where A is the tear strength in the M direction (kg / cm), and B is T
Direction tear strength (kg / cm), T is propylene-α-
Content of propylene-α-olefin copolymer rubber in olefin block copolymer (wt%), C is film thickness (μm) and D is content of α-olefin in propylene-α-olefin copolymer rubber Each represents the amount (wt%)) The M direction is the flow direction of the resin during molding, and the T direction is the direction perpendicular to the flow of the resin.
The value of {[(A × B) / T] / C} is preferably 0.5 to 260, and particularly preferably 1.0 to 230. 0.1
If it is less than 1, peeling occurs during drawing. On the other hand, if it exceeds 280, dents are formed on the metal plate during drawing, which is not preferable.

In the BPP of the present invention, the proportion of the copolymer rubber block in the copolymer is generally 20.
Is 70 to 70% by weight, preferably 25 to 68% by weight, and more preferably 30 to 65% by weight.

Further, as the BPP having excellent drawability, those having the following physical properties (a) and (b) are preferable. That is, (a) the para-xylene insoluble content at a temperature of 25 ° C. is in the range of 25 to 75% by weight, and (b) the para-xylene soluble content at a temperature of 25 ° C. is (i)
Average propylene content (FP) of 2 site model is 2
0 to 80 mol%, (ii) a copolymer (P) formed at an active site that preferentially polymerizes propylene in a two-site model
Percentage propylene content (P _P) is 65 to 90 mol% and the (iii) P _H of _H) occupied in the copolymer (P _f1) is zero.
It is in the range of 40 to 0.90.

(A) Para-xylene-insoluble matter means about 1% by weight of BPP dissolved in para-xylene at a temperature of 130.degree.
It is the insoluble matter when cooled to 25 ° C., and is the BP of the present invention.
The P content is preferably 25 to 75% by weight, and particularly preferably 30 to 70% by weight. Further, the (b) para-xylene soluble component is a component dissolved by the above-mentioned operation, and the properties obtained by the two-site model are preferably within the above range. Here, the two-site model of propylene-α-olefin will be described by taking a propylene-ethylene copolymer as an example. An example of a nuclear magnetic resonance ( ¹³ C-NMR) spectrum of isotope carbon of a propylene-ethylene copolymer is shown in FIG. In the spectrum, 10 peaks shown in (1) to (10) appear due to the difference in chain distribution (arrangement of ethylene and propylene). The name of this chain is Carman, C, J, et al; Macromo
lecules, Vol.10, p536-544 (1977), whose name is shown in FIG. Such a chain can be expressed as a reaction probability (P) assuming a reaction mechanism of copolymerization, and the relative intensities of the peaks of (1) to (10) when the overall peak intensity is set to 1 are P. It can be expressed as a probability equation by Bernoulli statistics with the parameter.

For example, in the case of (1) Sαα, if the propylene unit is the symbol p and the ethylene unit is the symbol e, the possible chains are [pppp], [pppe], and [epp].
e] and the reaction probability (P)
Express and add. The remaining peaks (2) to (10) can be obtained by formulating equations in a similar manner and optimizing P so that the peak intensity actually measured and those 10 equations are closest to each other. .

The two-site model is a model that assumes this reaction mechanism. HNCHENG; Jounal of Applied Polymer
Sience, Vol.35 p1639-1650 (1988). That is, in the model of copolymerizing propylene and ethylene using a catalyst, propylene content of the copolymer generated at the active sites of polymerization preferentially propylene _{(P H)} (P P)
Assuming two of the propylene content (P ' _P ) of the copolymer formed at the active site where ethylene and ethylene are preferentially polymerized,
_{When the} ratio of _H in the copolymer (P _f1 ) is used as a parameter, the probability equation shown in Table 1 below is obtained.

[0013]

[Table 1]

[0014] Therefore, the relative intensity of the ¹³ C-NMR spectrum as described above, P _P so that the probability equations shown in Table 1 are the same, by optimizing three parameters P _'P and P _f1 Desired.

The (i) average propylene content (FP) of the para-xylene solubles in the BPP of the present invention is determined by the following equation using the above three parameters. _{FP = P P × P f1 +} P 'P × (1-P f1) ( mol%) FP obtained by the above formula is preferably from 20 to 80 mol%, more preferably from 30 to 70 mol%.

Among the above parameters, (ii) P _P
Is preferably 65 to 90 mol%, and particularly preferably 70 to 85 mol%. Further, (iii) P _f1 is 0.40 to
0.90 is preferable, and 0.48 to 0.82 is particularly preferable.

The polymerization of BPP of the present invention is carried out in the presence of an inert hydrocarbon such as hexane, heptane, kerosene or a liquefied α-olefin solvent such as propylene in a slurry method,
The temperature condition is room temperature to 130 ° C., preferably 50 to 90 ° C., pressure 2 to 50, by a gas phase polymerization method in the absence of a solvent.
It is carried out under the condition of kg / cm ² . As the reactor in the polymerization step, those usually used in the technical field can be appropriately used, and examples thereof include a stirred tank reactor, a fluidized bed reactor, a circulation reactor, and a continuous type, a semi-batch type, or a batch type. Either method may be used.

Specifically, it can be obtained by using a known multistage polymerization method. That is, after polymerizing propylene and / or propylene-α-olefin copolymer in the first stage reaction,
This is a method of copolymerizing propylene and α-olefin in the second-stage reaction, and is disclosed in, for example, JP-A-3-97747 and JP-A-3-97747.
3-205439, JP-A-4-153203, JP-A-4-2614
23 and Japanese Patent Laid-Open No. 5-93024. Melt flow rate of BPP of the invention (JIS
According to K7210, measured in Table 1, condition 14) is appropriately selected depending on the molding method, but generally 0.2 to 20 g / 1.
0 minutes is used.

Further, the BPP of the present invention contains additives commonly used by those skilled in the art, such as an antioxidant, a weather resistance stabilizer, an antistatic agent, a lubricant, an antiblocking agent, an antifogging agent, and the like.
A pigment, a plasticizer, a softening agent and the like may be appropriately added within a range that does not impair the object of the present invention. The surface protective film of the present invention can be obtained by applying a known pressure-sensitive adhesive to a film obtained by subjecting the BPP to known inflation molding, T-die molding, calendaring, and the like. When used as a film, it may be used alone or may be laminated with other materials.

[0020]

The present invention will be described in more detail with reference to the following examples. In addition, the measuring method of each physical property is shown below. (Area-average particle size) The copolymer resin sample was dyed with RuO ₄ and then observed with a transmission electron microscope to obtain 30 μm × 3.
The area of 0 μm was randomly selected at 6 points, the particle diameters of all the particles existing in the area were measured, and the area average particle diameter D _S was calculated according to the following formula. D _S = ΣnD ² / ΣnD In the formula, n represents the number of particles having a particle diameter D. (Number average particle diameter) The number average particle diameter D _N was calculated by the following equation using the particle diameter measured by the above method. D _N = ΣnD / n

(Tear strength) The Elmendorf tear strength was determined according to JIS K7128B method. (Appearance of drawn product) Visually observe the drawn product,
The following three grades were used for evaluation. ○ ・ ・ ・ ・ No abnormalities △ ・ ・ ・ ・ Floating or breaking of film is very small × ・ ・ ・ ・ Floating or breaking of film is remarkable (Scratch condition) After drawing, peeling off the film, metal The presence or absence of dents on the surface of the plate was visually observed and evaluated according to the following three grades. ○ ・ ・ ・ ・ None △ ・ ・ ・ ・ Partially × ・ ・ ・ ・ Remarkable (Peelability) After forming a drawn product, it was left at room temperature for 2 weeks, but the film was peeled off, and the degree of difficulty at that time Was evaluated according to the following three grades. ○ ・ ・ ・ ・ Easy △ △ ・ ・ ・ Slightly difficult to peel × ・ ・ ・ ・ Peeling is difficult and requires force

(Analysis of Para-Xylene-Soluble Content by Two-Site Model) Para-Xylene-soluble content was subjected to ¹³ C-NMR spectrum measurement under the following apparatus and measurement conditions. ; Macromol
ecules, 13 , p267 (1980). Measuring device JNM-GSX400 manufactured by JEOL Ltd. Measurement mode: Proton decoupling method Pulse width: 8.0 μs Pulse repetition time: 5.0 s Cumulative number of times: 20000 Solvent: 1,2,4-trichlorobenzene /
Mixed solvent of deuterated benzene (75/25% by volume) Internal circulation: Hexamethyldisiloxane Sample concentration: 300 mg / 3.0 ml Solvent measurement temperature: 120 ° C. Next, a two-site model is analyzed to determine FP, _PP and P. _f1 was calculated.

Further, as a propylene-α-olefin block copolymer, polypropylene block and ethylene-
A block copolymer composed of a propylene copolymer block was used. The type (BPP1 to 8) and properties (area average particle diameter, number average particle diameter, proportion of copolymer rubber block, ethylene content in copolymer rubber, paraxylene insoluble matter, and paraxylene soluble matter FP, Table 2 shows P _P and P _f1 ).

Furthermore, 70 parts by weight of homopolypropylene (SA510 manufactured by Showa Denko KK) and an ethylene content of 7
30 parts by weight of 0% by weight of ethylene-propylene rubber was pelletized using a twin-screw extruder (hereinafter referred to as "PP /
"EPR") and the particle size thereof is shown in Table 2.

[0025]

[Table 2]

Examples 1 to 10 and Comparative Examples 1 to 8 BPP or PP / EPR shown in Table 2 was blown up to a thickness of 40 μm using a blow-up ratio of 2.0 using an inflation film molding machine manufactured by Placo. An 80 μm film was prepared. The tear strength was measured for each film. Also, an acrylic adhesive (main component; butyl acrylate) dissolved in toluene was applied to one surface of each of the obtained films so that the solid content would be about 3 μm, and dried at a temperature of 90 ° C. for 20 minutes. A protective film was obtained.

Then, the protective film was attached to a stainless plate (SUS304BA) having a thickness of 0.7 mm,
After applying a press oil (Japan Machine Oil G2960) to the film surface, a press molding machine (press pressure 600 kg / cm
² , container (vertical; 360mm, horizontal; press time 25 seconds)
450 mm, depth; 260 mm) was molded. The appearance, dent state and peelability of each of the obtained containers were evaluated. The above results are shown in Table 3.

[0028]

[Table 3]

[0029]

The surface protective film of the present invention is useful for surface protection of various materials because it has excellent drawability.

[Brief description of drawings]

FIG. 1 is an example of a nuclear magnetic resonance spectrum of isotope carbon of an ethylene-propylene copolymer.

FIG. 2 is a diagram showing names of carbons derived from a chain distribution in polyolefin.

Claims (3)

[Claims] 1. A surface protective film obtained by forming a pressure-sensitive adhesive layer on at least one side of a film substrate comprising a propylene-α-olefin block copolymer having the following physical properties (1) and (2). (1) The area average particle size of the propylene-α-olefin copolymer rubber particles dispersed in the polypropylene matrix phase is 1.5 μm or less, and the number average particle size is 1.0 μm.
m or less (2) The film substrate is in the range represented by the following formula: 0.1 ≦ {[(A × B) / T] / C} × D ≦ 280 (In the formula, A is the tear strength in the M direction. (Kg / cm), B is T
Direction tear strength (kg / cm), T is propylene-α-
Content of propylene-α-olefin copolymer rubber in olefin block copolymer (wt%), C is film thickness (μm) and D is content of α-olefin in propylene-α-olefin copolymer rubber Amount (% by weight) 2. A propylene-α-olefin block copolymer comprising a polypropylene block and a copolymer rubber block of propylene and an α-olefin having 2 to 12 carbon atoms (excluding 3), and the copolymerization. The surface protective film according to claim 1, wherein the proportion of the rubber block in the copolymer is 20 to 70% by weight. 3. The surface protective film according to claim 1, wherein the propylene-α-olefin block copolymer has the following physical properties (a) and (b). (A) Para-xylene insoluble matter at a temperature of 25 ° C.
75% by weight (b) Para-xylene-soluble matter at a temperature of 25 ° C is (i)
Average propylene content (FP) of 2 site model is 2
0 to 80 mol%, (ii) a copolymer (P) formed at an active site that preferentially polymerizes propylene in a two-site model
Percentage propylene content (P _P) is 65 to 90 mol% and the (iii) P _H of _H) occupied in the copolymer (P _f1) is zero.
40-0.90