JPH05140516A - Masking tape for automotive bumper - Google Patents

Abstract

PURPOSE:To obtain a masking tacky tape for automotive bumpers with suppressed formation of bubbles in a parting line of a tape edge without any adhesive remaining on a peeled surface after baking and drying. CONSTITUTION:The objective masking tacky tape for automotive bumpers is obtained by blending (A) 100 pts.wt. base polymer containing (A1) 45-95wt.% natural rubber, (A2) 0-25wt.% styrene-butadiene copolymer rubber and (A3) 5-30wt.% polyisoprene rubber with (B) 0-100 pts.wt., preferably 2-50 pts.wt. zinc oxide, (C) 20-150 pts.wt., preferably 30-100 pts.wt. tackifier resin (e.g. a rosin-baged or a terpenic resin), (D) 0.05-7 pts.wt. thiuram-based compound (e.g. tetramethylthiuram disulfide) and (E) 0.05-10 pts.wt. one or more compounds selected from dithiocarbamate-based compounds, xanthogenate-based compounds and thiazole-based compounds, and applying the resultant tacky agent composition onto a flexible polyvinyl chloride film. The apparent viscosity of the tacky agent composition calculated by using the formula [eta is the apparent viscosity (P); S is the application area (cm<2>); W is the load (stress) (g); (h) is the thickness (cm) of the tacky agent layer; D is the flow velocity (cm/sec)] is 0.5X10<7> to 1X10<8> P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a masking pressure-sensitive adhesive tape used for coating automobile bumpers. The present invention relates to a good masking pressure-sensitive adhesive tape for automobile bumpers, which has no sticking marks.

[0002]

2. Description of the Related Art In order to enhance the appearance and appearance of automobile bodies, various coating methods are applied to bumpers, vehicle body skins and the like. Bumpers are made plastic and color-finished as automobiles become lighter.

When separately coating the bumper of an automobile,
Various types of masking adhesive tapes are used, but the demand level for coating film quality is increasing, and as technological development of coating methods progresses, the demand for higher performance and diversification of masking adhesive tapes is increasing. ..

Specific performance requirements for masking adhesive tapes for automobile bumpers include, for example, (1) having sufficient adhesive strength at room temperature (adhesiveness), (2) not peeling off during baking and drying of paint at high temperature. That (heat resistance),
(3) The adhesive does not remain on the tape peeling surface after baking and drying, (4) the parting line of the coating film of the masking part can be clearly displayed (parting property), (5) the adherend is not contaminated ( Non-polluting), and the like.

By the way, since the adherend to be masked is usually a curved surface containing irregularities, the support of the adhesive tape is required to have a certain degree of elongation or more. Therefore, conventionally, a crepe tape using crepe paper as a support has been mainly used for two-tone painting of automobile bumpers. A rubber-based pressure-sensitive adhesive has been mainly used as an adhesive for the masking adhesive tape. However, the crepe tape has a problem that the parting line cannot be finished clearly. Moreover, the crepe tape cannot sufficiently follow the expansion of the bumper during heating and the contraction of the bumper during cooling in the baking / drying process after painting the plastic bumper, which may cause warpage in the bumper. is there.

Therefore, recently, a masking adhesive tape using a plastic film, particularly a soft polyvinyl chloride film, has come to be used as a support capable of following the expansion and contraction of the plastic bumper in the baking and drying process.

However, when a masking pressure-sensitive adhesive tape using a soft polyvinyl chloride film as a support is used for coating, air bubbles (so-called "armpits") are likely to occur in the coating film at the parting line of the tape edge. .. With a masking adhesive tape that uses crepe paper as a support, even if gas is generated due to the organic solvent or low boiling point substances contained in the adhesive layer or adherend, it will pass through the fine pores of the crepe paper when heated. Although it is discharged, in the case of a masking adhesive tape made of a soft polyvinyl chloride film, since it does not have such fine holes, the gas accumulated under the tape is discharged from the tape edge, and therefore the tape edge cutoff line. Bubbles are formed in the coating film applied to the area.

After the masking pressure-sensitive adhesive tape is peeled off, the air bubbles remain as voids in the coating film, impairing the appearance of the coating film, and when the top coat is further applied, these voids cause the generation of new bubbles, and the top coat Bubbles are generated in the coating film.

[0009] Conventionally, in order to prevent the deterioration of the appearance due to such air bubbles, a two-component acrylic / isocyanate clear paint is applied to the entire surface or only the parting line portion of the applied paint film after applying the paint separately. A method of coating and baking and curing has been proposed (JP-A 1-2).
03079, JP-A 1-203085). However, in the present situation, a masking tape using a soft polyvinyl chloride film as a support has not been found to be an effective means for preventing or suppressing the formation of bubbles.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a masking pressure-sensitive adhesive tape using a soft polyvinyl chloride film as a support, which suppresses the formation of bubbles in the parting line of the tape edge and is baked and dried. An object of the present invention is to provide a masking pressure-sensitive adhesive tape for automobile bumpers in which no pressure-sensitive adhesive remains on the peeling surface afterwards.

As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have found that a rubber-based pressure-sensitive adhesive is a pressure-sensitive adhesive (adhesive) unless it is crosslinked with a crosslinking agent. It was found that when the degree of cross-linking is too high, on the contrary, the residue disappears, but the tackiness at high temperature decreases and the cut-off property decreases.

Further, as a result of research, as a base polymer of a rubber-based pressure-sensitive adhesive for masking pressure-sensitive adhesive tape, a specific elastomer was used in combination in a specific amount ratio, and a specific crosslinking agent was used in an appropriate amount. It has been found that by crosslinking with, even when a soft polyvinyl chloride film is used as a support, generation of bubbles at the tape edge is prevented or suppressed, and a clear parting line can be obtained. In the masking pressure-sensitive adhesive tape using this pressure-sensitive adhesive composition, the pressure-sensitive adhesive does not remain on the tape peeling surface after baking and drying.

The reason why the use of the masking adhesive tape of the present invention prevents or suppresses the generation of bubbles is that an organic solvent or other low-boiling-point gas that normally vaporizes during heating temporarily adheres. It is presumed that this is because it is sorbed by the agent composition and is suppressed from being discharged to the outside of the system. The present invention has been completed based on these findings.

[0014]

Thus, according to the present invention, (A) 45-95% by weight of natural rubber, styrene-
Based on 100 parts by weight of a base polymer containing 0 to 25% by weight of butadiene copolymer rubber and 5 to 30% by weight of polyisobutylene rubber, (B) 0 to 100 parts by weight of zinc oxide and (C) 20 to 150 of tackifying resin. Parts by weight, (D) thiuram compound 0.05 to 7 parts by weight, and (E) at least one compound selected from the group consisting of dithiocarbamate compound, xanthogenate compound and thiazole compound 0.05 to There is provided a masking pressure-sensitive adhesive tape for an automobile bumper, comprising a soft polyvinyl chloride film coated with a pressure-sensitive adhesive composition containing 10 parts by weight.

The masking adhesive tape of the present invention means both an adhesive tape and an adhesive sheet.

The present invention will be described in detail below. (Base Polymer) In the present invention, natural rubber and polyisobutylene rubber are used as essential components as a base polymer of the pressure-sensitive adhesive composition (pressure-sensitive adhesive), and styrene-butadiene copolymer rubber is optionally used in combination.

As the natural rubber used in the present invention,
Commonly used ribbed smoked sheets, air dry sheets, pale crepes and the like are used. Natural rubber is usually masticated so as to have an appropriate molecular weight.

The proportion of natural rubber used is 45 to 95% by weight in the base polymer. If the content of natural rubber is less than 45% by weight, good tack cannot be obtained and 95% by weight
If it exceeds the limit, the apparent viscosity of the pressure-sensitive adhesive composition at 90 ° C. does not decrease, and the parting property during coating deteriorates.

The styrene-butadiene copolymer rubber used in the present invention is a random copolymer, a block copolymer,
Although any graft copolymer may be used, a random copolymer is preferable from the viewpoint of adhesive properties. These may be synthesized, but commercially available products can be used.

The random copolymers are Nipol 1500 and Nipol 150 manufactured by Nippon Zeon Co., Ltd.
2, Nipol 1507, Nipol 1006, Nipol 1
009, Nipol 2000; trade name JSR1500, JSR1502, JSR150 manufactured by Nippon Synthetic Rubber Co., Ltd.
3, JSR1013N, JSR0202 and the like. As the block copolymer, trade names TR1101, TR1118, TR4122S, TR manufactured by Shell Chemical Co., Ltd.
KX138S; trade name Tuftec H manufactured by Asahi Kasei Co., Ltd., and the like. As the graft copolymer, trade names TR1122, TR1116, and TR420 manufactured by Shell Chemical Co., Ltd.
5S etc. are mentioned.

The styrene-butadiene copolymer rubber may be added without any addition, but the addition thereof has the effect of lowering the apparent viscosity at 90 ° C. The proportion of the styrene-butadiene copolymer rubber used is 0 to 25% by weight in the pace polymer. If the usage ratio exceeds 25% by weight, good tack cannot be obtained.

Polyisobutylene rubber, when added to the base polymer, has the effects of improving the durability of the pressure-sensitive adhesive composition, suppressing the floating of the masking pressure-sensitive adhesive tape at high temperatures, and further reducing the apparent viscosity at 90 ° C. .. The proportion of polyisobutylene rubber used is 5 to 30% by weight in the base polymer. If this usage ratio is less than 5% by weight, the apparent viscosity of the pressure-sensitive adhesive composition at 90 ° C. does not decrease and the cut-off property decreases. If it exceeds 30% by weight, the pressure-sensitive adhesive composition undergoes phase separation, and a uniform composition cannot be obtained.

The polyisobutylene rubber may be synthesized, or a commercially available product may be used. Examples of commercially available products include Vistanex LM-MH under the trade name of Exxon Co.,
Vistanex MM-L-80, Vistanex MM-
L-100, Vistanex MM-L120, Vistanex MM-L-140; trade name Opanol B-10, Opanol B-80, Opanol B-120 of Basuf Company.
Etc.

(Zinc Oxide) Zinc oxide (zinc white) is not necessarily used, but since it acts as an activating aid in sulfur-free vulcanization, its incorporation accelerates the crosslinking reaction.

The proportion of zinc oxide used is based on the base polymer 1
0 to 100 parts by weight, preferably 1 to 100 parts by weight
80 parts by weight, more preferably 2 to 50 parts by weight.
If this proportion exceeds 100 parts by weight, the kneading operation becomes difficult and the tackiness of the adhesive tape is reduced. Zinc oxide is usually used by kneading it with a base polymer using an open roll, a pressure kneader, a Banbury mixer or the like.

(Tackifying Resin) The tackifying resin is used in a proportion of 20 to 150 parts by weight, preferably 30 to 100 parts by weight, based on 100 parts by weight of the base polymer. If the usage ratio is less than 20 parts by weight, sufficient tackiness cannot be obtained, and conversely, if it exceeds 150 parts by weight, tack is lowered.

Examples of the tackifying resin include natural products such as rosin resin and terpene resin and derivatives thereof; aliphatic petroleum resin, alicyclic petroleum resin, aromatic petroleum resin, coumarone indene resin, Examples thereof include synthetic resins such as styrene resins, phenol resins, and xylene resins; these are used alone or in combination of two or more kinds.

Examples of the rosin resin include rosin, polymerized rosin, hydrogenated rosin, rosin ester, hydrogenated rosin ester, and rosin phenol resin. As a rosin,
Gum rosin, tall oil rosin, wood rosin (manufactured by Hercules, USA) and the like can be mentioned. Examples of the polymerized rosin include polypeel resin and Daimalex resin (manufactured by Rika Hercules). Examples of the hydrogenated rosin include steberite and Foral AX (manufactured by Rika Hercules). As the rosin ester, ester gum A, ester gum AAV (manufactured by Arakawa Chemical Co., Ltd.), Harrier Star T, Harrier Star S (manufactured by Harima Kasei Co.), ester gum 8L, pentaline A (manufactured by Rika Hercules Co., Ltd.)
Etc. Examples of the hydrogenated rosin ester include ester gum H, ester gum HP (manufactured by Arakawa Chemical Co., Ltd.), pentaline H, Foral 85, Foral 105 (manufactured by Rika Hercules) and the like. Examples of the rosin phenol resin include Sumirite resin PR12603 (manufactured by Sumitomo Durez Co., Ltd.) and Tamanor 803 (manufactured by Arakawa Chemical Co., Ltd.).

As the terpene resin, a terpene resin,
There are terpene phenol resin, aromatic modified terpene resin and the like. Examples of the terpene resin include YS resin Px (produced by Yasuhara Yushi Co., Ltd.) and Piccolite A (produced by Hercules Co., Ltd.). As terpene phenol resin, YS Polystar T, Schenectady SP566 [Schenec
Tady (Schenectady), USA] and the like. As aromatic modified terpene resin, YS resin TO
(Made by Yasuhara Yushi Co., Ltd.) and the like.

Examples of the aliphatic petroleum resin include Picco Pail (manufactured by Hercules), Escorets (manufactured by Esso Kagaku), Wing Tack 95 (manufactured by Goodyear, USA), Hilets (Mitsui Petrochemicals), Quinton A.
(Manufactured by Zeon Corporation), Marukalets (manufactured by Maruzen Petrochemical Co., Ltd.), Coporex (manufactured by Toho Petroleum Resin Co., Ltd.) and the like. Examples of the alicyclic petroleum resin include Alcon P and Alcon M (manufactured by Arakawa Chemical Co., Ltd.). Examples of the aromatic petroleum resin include petrozine (manufactured by Mitsui Petrochemical Co., Ltd.) and high resin (manufactured by Toho Petroleum Resin Co., Ltd.).

Examples of the coumarone indene resin include coumarone NG (Nippon Steel Chemical). Examples of the styrene resin include piccolastic A (manufactured by Hercules). Examples of the phenol resin include hitanol (manufactured by Hitachi Chemical Co., Ltd.), tacky roll (manufactured by Sumitomo Chemical Co., Ltd.), and resin top (manufactured by Gunei Chemical Industry Co., Ltd.). Examples of the xylene resin include Nikanol (manufactured by Mitsubishi Gas Chemical Co., Inc.) and the like.

(Crosslinking Agent) In the present invention, a crosslinking agent (vulcanization accelerator) such as a thiuram compound is used to crosslink the base polymer by sulfur-free vulcanization.

The thiuram compound is a component that crosslinks the pressure-sensitive adhesive, and is 0.0 to 100 parts by weight of the base polymer.
It is used in a proportion of 5 to 7 parts by weight. This usage rate is 0.0
If it is less than 5 parts by weight, solvent resistance and heat resistance are deteriorated, and the pressure-sensitive adhesive tends to remain. Further, if it exceeds 7 parts by weight, the crosslink density becomes high, so that the solvent resistance and the heat resistance are improved, but the tackiness at a high temperature and the sorption property of the solvent are lowered and the parting property is lowered.

Examples of the thiuram compound include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram monosulfide, tetrabutylthiuram disulfide, tetramethylthiuram monosulfide, N, N'-dimethyl-N, N'-diphenylthiuram disulfide. , Dipentamethylene thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide, dicyclopentamethylene thiuram disulfide and the like.

The dithiocarbamate-based compound, the xanthogenate-based compound and the thiazole-based compound have the action of promoting the crosslinking reaction, and are used alone or in combination of two or more kinds. The use ratio of these components is 0.05 to 10 parts by weight based on 100 parts by weight of the base polymer. This usage rate is 0.0
If it is less than 5 parts by weight, its effect is low, and if it exceeds 10 parts by weight, the adherend is contaminated, which is not preferable.

As the dithiocarbamate compound,
Pentamethylenedithiocarbamic acid piperidine salt, pipecolyl dithiocarbamic acid pipecoline salt, lead dimethyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc dimethylpentamethylenedithiocarbamate, lead ethylphenyldithiocarbamate, potassium dimethyldithiocarbamate, potassium dibutyldithiocarbamate , Selenium dimethyldithiocarbamate, selenium diethyldithiocarbamate, bismuth dimethyldithiocarbamate, zinc dimethyldithiocarbamate,
Zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dibutyldithiocarbamate, Examples thereof include copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, and tellurium diethyldithiocarbamate.

Examples of the xanthate-based compound include zinc butylxanthate, zinc isopropylxanthate, sodium isopropylxanthogenate, zinc ethylxanthate, dibutylxanthogen disulfide and the like.

Examples of thiazole compounds include 2-mercaptobenzothiazole, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2-mercaptobenzothiazole zinc salt, 2-mercaptobenzothiazole copper salt, 2-mercaptobenzothiazole sodium salt, and 2 −
(2 ', 4'-Dinitrophenylthio) benzothiazole, 2-mercaptobenzothiazolecyclohexylamine salt, 2- (N, N-diethylthiocarbamoylthio) benzothiazole, 2- (2,6-dimethyl-4-)
Examples thereof include morpholinothio) benzothiazole and 2- (4'-morpholinodithio) benzothiazole.

(Masking Adhesive Tape) The adhesive composition used in the present invention contains the above-mentioned components. In addition to the above, for example, phenol-based, amine-based, thioether-based, phosphite-based, etc. Antiaging agents, softeners, plasticizers, fillers other than zinc white, colorants and the like can be added as required.

The adhesive composition is dissolved in, for example, one or more organic solvents such as toluene, hexane, heptane, methyl ethyl ketone, acetone, methanol, isopropanol, ethyl acetate, butyl acetate, etc., and the resulting solution is supported. It is coated on a soft polyvinyl chloride film on the body, dried and crosslinked. An organic solvent solution of the pressure-sensitive adhesive composition may be applied on release paper in advance to form a pressure-sensitive adhesive composition layer, and then the layer may be transferred onto a soft polyvinyl chloride film. The soft polyvinyl chloride film is not particularly limited, and those commonly used in this field are used.

The crosslinking of the base polymer is preferably carried out simultaneously with the drying of the pressure-sensitive adhesive composition layer. This drying / crosslinking is usually performed by heating at 80 to 150 ° C. for 1 to 5 minutes. When the crosslinking is insufficient, the adhesive tape may be wound into a roll and post-crosslinked at 40 to 150 ° C. for 1 hour to 1 week.

The masking pressure-sensitive adhesive tape for automobile bumpers thus obtained is JIS-Z-0237-11.
When the apparent viscosity of the pressure-sensitive adhesive composition is measured under the conditions according to the measuring method of the holding force specified in the paragraph, the apparent viscosity at 90 ° C. calculated by the formula [I] is 0.5 × 1.
It is preferably in the range of 0 ⁷ to 1 × 10 ⁸ poise.
If the apparent viscosity at 90 ° C. is less than 0.5 × 10 ⁷ poises, when peeled after baking and drying, result in residual adhesive on the adherend member surface, the coating of the parting property exceeds 1 × 10 ⁸ poise in the opposite Becomes worse.

Η = [W / S × 980] · h / D [I] η: Apparent viscosity (poise) S: Application area (cm ² ) W: Load (stress) (g) h: Thickness of adhesive layer (Cm) D: Flow rate (cm / sec) [W / S × 980] is shear stress (dyne / cm ² ).
Indicates. Further, the flow velocity D is calculated by reading the deviation distance Δx at every predetermined time interval t and calculating the average value thereof.

Specifically, cleaned stainless steel (SU
S304) The test plate is attached so that the area of 25 × 25 mm of the test piece is in contact with the test plate, and the non-attached portion is folded over with the inner surface facing inward. The test piece is pressed back and forth once with a roller at a crimping speed of about 300 mm / min. The test piece is heated to the measurement temperature of 90 ° C. Make the test piece hang vertically and put 100
Attach a weight of 0 g and apply the load. Then 5
After a second, the start point is read, the shift distance (Δx) of the test piece is read at predetermined time intervals (60 seconds), and the flow velocity D is calculated from the average value of the five points.

[0045]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The blending amount is part by weight unless otherwise specified.

The methods for measuring the physical properties are as follows. <Viscosity> The apparent viscosity at 90 ° C. (unit: × 10 ⁷ poise) was measured by the above method.

<Solvent resistance> Adhesive tape test piece (15 m
(m × 30 mm) was immersed in toluene, the dissolved state was observed after 5 minutes, and evaluation was made according to the following three grades. ×: dissolved, Δ: partially dissolved, ◯: not dissolved.

<Discontinuity> A polypropylene plate is washed with trichloroethane, then an adhesive tape is attached, and then a urethane-based paint (product name of Nippon Bee Chemical Co., Ltd., trade name)
RB115) was sprayed so that the thickness after drying was 15 μm. After drying at 120 ° C. for 20 minutes, the generation state of bubbles in the coating film at the tape edge portion was visually observed and evaluated in the following three stages. ×: There are many bubbles, Δ: There are some bubbles, ◯: No bubbles.

<Pasting trace> After washing the polypropylene plate with trichloroethane, a urethane-based paint is sprayed so that the thickness after drying is 15 μm, and then the temperature is 120 ° C. for 20 minutes.
A test plate was prepared by drying for a minute. An adhesive tape is attached to this, and after heating at 120 ° C. for 20 minutes, the adhesive tape is peeled off, and the state of the peeled mark on the peeled surface is visually observed,
The following three grades were used for evaluation. X: A large amount of adhesive residue is left, Δ: A little adhesive residue is left, ◯: No adhesive residue is left.

<Tack> Measured by the ball rolling method of JIS Z-0237 12, and evaluated by the following standard by ball number. ×: less than ball number 5, ○: more than ball number 5.

[Examples 1 and 2, Comparative Examples 1 and 2] Zinc white was kneaded into natural rubber with an open roll and masticated, and then stirred together with the components shown in Table 1 in a toluene / methanol mixed solvent. While dissolving.

The obtained solution was applied to a soft polyvinyl chloride film (thickness 40 μm), dried at 80 ° C. for 5 minutes and crosslinked. Then, the adhesive tape was wound on a roll and left at 60 ° C. for 24 hours for post-crosslinking. The dry thickness of the pressure-sensitive adhesive composition layer was 32 μm. The results are shown in Table 1.

The components in Table 1 are as follows. <NR> Natural rubber; Natural rubber (NR) was prepared by previously kneading zinc white with an open roll. Zinc white was blended so as to be 10 parts with respect to 100 parts of the base polymer. However, Table 1 shows only the NR component. <SBR> styrene-butadiene copolymer rubber; manufactured by Nippon Zeon Co., Ltd., Nipol 1006 <PIB> polyisobutylene rubber; manufactured by Exxon, Vistanex MM-L-100 <ESCOLETS> aliphatic petroleum tree; manufactured by Esso Chemical Co., Ltd. <TBT> Tetrabutyl thiuram disulfide (thiuram compound) <ZBX> Zinc butylxanthate (xanthogenic acid compound) <M> 2-Mercaptobenzothiazole (thiazole compound)

[0054]

[Table 1]

Incidentally, the pressure-sensitive adhesive composition solution of Comparative Example 2 could not be prepared into a test piece because of phase separation.

[Examples 3 to 4 and Comparative Example 3] Example 1 except that the pressure-sensitive adhesive composition having the formulation shown in Table 2 was used.
An adhesive tape was prepared in the same manner as above and evaluated in the same manner. The results are shown in Table 2.

[0057]

[Table 2]

[Example 5] Using the masking pressure-sensitive adhesive tapes prepared in Examples 1 to 4, coating experiments of polypropylene bumpers (PP bumpers) were actually conducted.

After washing the PP bumper with an organic solvent and air-drying, a masking adhesive tape was attached. A primer is applied and dried at 120 ° C for 20 minutes, and then a urethane-based paint (trade name RB11 manufactured by Nippon Bee Chemical Co., Ltd.)
5) was spray-painted and dried at 120 ° C. for 20 minutes, and then the adhesive tape was peeled off.

Tests were carried out by using 25 bumpers each by the above method, and the residual adhesive and the parting property were evaluated.

The adhesive remaining and the parting property were evaluated according to the following five grades. ⊚: The parting property is very good, and no adhesive remains. ◯: The parting property is good and there is no adhesive residue. Δ: Some bubbles are generated on the parting line, but they can be easily repaired, and some adhesive remains, but it can be easily removed. ×: Some bubbles were generated on the parting line, and some adhesive remained. XX: Bubbles were generated on the parting line, and the amount of adhesive remained so that the bumper had to be discarded. is there.

[0062]

[Table 3]

[0063]

According to the present invention, it is possible to provide a good masking pressure-sensitive adhesive tape for automobile bumpers, which has an excellent parting property of the paint masking and has no residue or sticking of the pressure-sensitive adhesive.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Wakabayashi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (2)

[Claims] 1. (A) 45 to 95% by weight of natural rubber,
Based on 100 parts by weight of a base polymer containing 0 to 25% by weight of styrene-butadiene copolymer rubber and 5 to 30% by weight of polyisobutylene rubber, (B) zinc oxide 0 to
From 100 parts by weight, (C) tackifying resin 20 to 150 parts by weight, (D) thiuram-based compound 0.05 to 7 parts by weight, and (E) dithiocarbamate-based compound, xanthate-based compound and thiazole-based compound A masking pressure-sensitive adhesive tape for automobile bumpers, comprising a soft polyvinyl chloride film coated with a pressure-sensitive adhesive composition containing at least one compound selected from the group consisting of 0.05 to 10 parts by weight. 2. The adhesive tape as a test piece,
When the apparent viscosity is measured under the conditions according to the method for measuring the holding force defined in IS-Z-0237 item 11,
The masking pressure-sensitive adhesive tape for an automobile bumper according to claim 1, wherein the apparent viscosity at 90 ° C. calculated by the following formula [I] is in the range of 0.5 × 10 ⁷ to 1 × 10 ⁸ poise. η = [W / S × 980] · h / D [I] η: Apparent viscosity (poise) S: Application area (cm ² ) W: Load (stress) (g) h: Thickness of adhesive layer (cm) ) D: Flow rate (cm / sec)