Acrylic resin film having excellent resistance to whitening on bending and excellent cracking resistance

Abstract

Disclosed herein is an acrylic resin film that is less likely to whiten on bending when laminated on a plastic molded body or the like, has well-balanced physical properties such as high surface hardness, excellent transparency, and excellent cracking resistance, and is therefore suitable for use in decorative molding. The acrylic resin film is obtained by forming, into a film, a methacrylic resin composition (D) containing a specific methacrylate-based resin (A), a rubber-containing four-stage graft copolymer (B) containing rubber particles having an average particle size of 0.2 to 0.4 m, and a rubber-containing two-layer graft copolymer (C) containing rubber particles having an average particle size of 0.02 to 0.15 m.

Claims

1. An acrylic resin film obtained by forming, into a film, a methacrylic resin composition (D) containing the following components (A) to (C): a methacrylate-based resin (A) obtained by polymerizing 50 to 100 wt % of a methacrylate and 0 to 50 wt % of at least one monomer copolymerizable therewith; a rubber-containing graft copolymer (B) obtained by polymerizing only the following monomer components (B-1), (B-2), (B-3), and (B-4) in this order so that rubber particles that are a polymerization product of the monomer components (B-1) and (B-2) have an average particle size of 0.2 to 0.4 m: a monomer component (B-1) comprising 60 to 100 wt % of a methacrylate (b-1-1), 40 to 0 wt % of a monofunctional monomer (b-1-2) copolymerizable therewith, and 0.05 to 10 parts by weight of a polyfunctional monomer (b-1-3) with respect to 100 parts by weight of (b-1-1)+(b-1-2); a monomer component (B-2) comprising 50 to 100 wt % of an acrylate (b-2-1), 50 to 0 wt % of a monofunctional monomer (b-2-2) copolymerizable therewith, and 0.05 to 10 parts by weight of a polyfunctional monomer (b-2-3) with respect to 100 parts by weight of (b-2-1)+(b-2-2); a monomer component (B-3) comprising 80 to 100 wt % of a methacrylate (b-3-1) and 20 to 0 wt % of a monofunctional monomer (b-3-2) copolymerizable therewith, and no polyfunctional monomer, the monofunctional monomer (b-3-2) being an acrylate; and a monomer component (B-4) comprising 20 to 70 wt % of a methacrylate (b-4-1) and 80 to 30 wt % of a monofunctional monomer (b-4-2) copolymerizable therewith, the monofunctional monomer (b-4-2) being an acrylate; and a rubber-containing graft copolymer (C) that is a two-layer polymer obtained by polymerizing the following monomer components (C-1) and (C-2) in this order so that rubber particles that are a polymerization product of the monomer component (C-1) have an average particle size of 0.02 to 0.15 m: a monomer component (C-1) comprising 50 to 100 wt % of an acrylate (c-1-1), 50 to 0 wt % of a methacrylate (c-1-2), and 0.05 to 10 parts by weight of a polyfunctional monomer (c-1-3) (with respect to 100 parts by weight of (c-1-1)+(c-1-2)); and a monomer component (C-2) comprising 50 to 100 wt % of a methacrylate (c-2-1) and 50 to 0 wt % of a monofunctional monomer (c-2-2) copolymerizable therewith, wherein a weight ratio of the monomer component (B-4) is more than 5% by weight and less than 30% by weight per 100 wt % of a total weight of the monomer components (B-1) to (B-4).

2. The acrylic resin film according to claim 1, wherein the methacrylic resin composition (D) contains 1 to 20 parts by weight of the rubber particles that are a polymerization product of the monomer components (B-1) and (B-2) and 1 to 50 parts by weight of the rubber particles that are a polymerization product of the monomer component (C-1) per 100 parts by weight of the methacrylic resin composition (D).

3. The acrylic resin film according to claim 1, wherein the monomer component (C-1) satisfies the following formula (1):
20dw125d(1) wherein d is an average particle size (m) of the rubber particles that are a polymerization product of the monomer component (C-1) and w is the number of parts by weight of the polyfunctional monomer (c-1-3) (with respect to 100 parts by weight of (c-1-1)+(c-1-2)).

4. The acrylic resin film according claim 1, which has a film thickness of 30 to 500 m.

5. The acrylic resin film according to claim 1, which has a coating layer on its at least one surface.

6. The acrylic resin film according to claim 1, which has a hard coat layer on its one surface and has a primer layer on its surface opposite to the one surface.

7. The acrylic resin film according to claim 6, wherein the hard coat layer is formed by curing at least one selected from the group consisting of a urethane acrylate-based resin, an acrylate-based resin, and a silicone-based resin.

8. The acrylic resin film according to claim 6, wherein the hard coat layer has a surface hardness of HB or more.

9. A molded article made of the acrylic resin film according to claim 1.

10. A laminate obtained by laminating the acrylic resin film according to claim 1 on a base material.

11. The acrylic resin film according to claim 1, wherein the monomer component (B-4) comprising 30 to 70 wt % of a methacrylate (b-4-1) and 70 to 30 wt % of a monofunctional monomer (b-4-2) copolymerizable therewith, the monofunctional monomer (b-4-2) being an acrylate.

Description

EXAMPLES

(1) Hereinbelow, the present invention will be described in more detail based on examples, but is not limited to these examples.

(2) It is to be noted that in the following production examples, examples, and comparative examples, part(s) and % represent part(s) by weight and % by weight, respectively.

(3) Abbreviations for substances are as follows.

(4) BA: n-butyl acrylate

(5) MMA: methyl methacrylate

(6) St: styrene

(7) AIMA: allyl methacrylate

(8) It is to be noted that in the following examples and comparative examples, measurements of physical properties were performed by the following methods.

Evaluation of Polymerization Conversion Rate

(9) A latex obtained by polymerization was dried at 120 C. for 1 hour in a hot air drier to determine its solid content, and a polymerization conversion rate (%) was calculated by 100solid content/amount of monomer charged.

Evaluation of Average Particle Size of Rubber Particles

(10) A compound obtained by blending the rubber-containing graft copolymer (B) (or the rubber-containing graft copolymer (C)) and SUMIPEX EX (manufactured by Sumitomo Chemical Company, Limited) in a 50:50 ratio was molded to obtain a film, and the micrograph of the film was taken by a RuO.sub.4 staining and ultrathin sectioning method with a transmission electron microscope (JEM-1200EX manufactured by JEOL Ltd.) at an accelerating voltage of 80 kV. Then, 100 images of rubber particles were randomly selected from the obtained micrograph, and the average of their particle sizes was determined.

Evaluation of Haze

(11) The transparency of the obtained film was evaluated by measuring the haze of the film in accordance with JIS K6714 at a temperature of 23 C.2 C. and a humidity of 50%5%.

Evaluation of Pencil Hardness

(12) The pencil hardness of the obtained film was measured in accordance with JIS K5600-5-4.

Evaluation of Cracking Resistance

(13) The film was cut with a utility knife and evaluated according to the following criteria:

(14) A: the occurrence of cracking was not observed in cut surfaces;

(15) B: the occurrence of cracking was observed in cut surfaces; and

(16) C: the occurrence of cracking was significantly observed in cut surfaces.

Resistance to Whitening on Bending

(17) The film was bent at 180 at 23 C. and observed to evaluate whether the whitening of the film occurred according to the following criteria:

(18) A: whitening was not observed;

(19) B: whitening was slightly observed; and

(20) C: whitening was significantly observed.

Tensile Elongation at 120 C.

(21) The tensile elongation of the film having a coating layer was measured with a Tensilon tensile tester equipped with a thermostatic chamber at 120 C. under conditions of a distance between chucks of 50 mm and a tension rate of 200 mm/min to determine the elongation at the time when the coating layer could not follow the elongation of the acrylic resin film so that cracking occurred in the coating layer.

Production Example 1

Production of Rubber-Containing Graft Copolymer (B1)

Preparation of Innermost-Layer Polymer

(22) A mixture having the following composition was charged into a glass reactor and heated to 80 C. with stirring in a nitrogen stream, and then 25% of a mixed liquid of a monomer mixture composed of 25 parts of methyl methacrylate and 1 part of allyl methacrylate (shown as (B-1) of Production Example 1 in Table 1) and 0.1 parts of t-butyl hydroperoxide was charged into the reactor at once to perform polymerization for 45 minutes.

(23) TABLE-US-00001 Deionized water 220 parts Boric acid 0.3 parts Sodium carbonate 0.03 parts Sodium N-lauroyl sarcosinate 0.09 parts Sodium formaldehyde sulfoxylate 0.09 parts Disodium ethylenediaminetetraacetate 0.006 parts Ferrous sulfate 0.002 parts

(24) Then, remaining 75% of the mixed liquid was continuously added over 1 hour. After the completion of the addition, the mixture was kept at the same temperature for 2 hours to complete the polymerization. During this time, 0.2 parts of sodium N-lauroyl sarcosinate was added. The polymerization conversion rate (amount of polymer formed/amount of monomer charged) of the thus obtained innermost-layer cross-linked methacrylic polymer latex was 98%.

Preparation of Rubber Particles

(25) The obtained innermost-layer polymer latex was kept at 80 C. in a nitrogen stream, 0.1 parts of potassium persulfate was added, and then a monomer mixture composed of 41 parts of n-butyl acrylate, 9 parts of styrene, and 1 part of allyl methacrylate (shown as (B-2) of Production Example 1 in Table 1) was continuously added over 5 hours. During this time, 0.1 parts of potassium oleate was added in three parts. After the completion of the addition of the monomer mixed liquid, 0.05 parts of potassium persulfate was further added and the mixture was kept for 2 hours to complete polymerization, obtaining a latex of rubber particles. The polymerization conversion rate of the obtained rubber particles was 99%.

Preparation of Graft Copolymer

(26) The obtained latex of rubber particles was kept at 80 C., 0.02 parts of potassium persulfate was added, and then a monomer mixture composed of 14 parts of methyl methacrylate and 1 part of n-butyl acrylate (shown as (B-3) of Production Example 1 in Table 1) was continuously added over 1 hour. After the completion of the addition of the monomer mixed liquid, the mixture was kept for 1 hour to obtain a graft copolymer latex. The polymerization conversion rate of the graft copolymer latex was 99%.

Preparation of Rubber-Containing Graft Copolymer

(27) The obtained latex of rubber particles was kept at 80 C., and a monomer mixture of 5 parts of methyl methacrylate and 5 parts of n-butyl acrylate (shown as (B-4) of Production Example B1 in Table 1) was continuously added over 0.5 hours. After the completion of the addition of the monomer mixed liquid, the mixture was kept for 1 hour to obtain a rubber-containing graft copolymer latex. The polymerization conversion rate of the rubber-containing graft copolymer latex was 99%.

(28) The obtained rubber-containing graft copolymer latex was subjected to salting-out and coagulation with calcium chloride, heat treatment, and drying to obtain a white powder of a rubber-containing graft copolymer (B1).

Production Examples 2 to 4

(29) Rubber-containing graft copolymers (B2) to (B4) were obtained in the same manner as in Production Example 1 except that the compositions of the monomer components (B-1) to (B-4) were changed as shown in Table 1.

(30) TABLE-US-00002 TABLE 1 Production Examples Rubber-containing 1 2 3 4 graft copolymer B1 B2 B3 B4 Monomer (B-1) MMA 25 10 25 25 mixture BA 0 15 0 0 (part (s)) AIMA 1 1 1 1 (B-2) BA 41 41 41 41 St 9 9 9 9 AIMA 1 1 1 1 (B-3) MMA 14 14 14 19 BA 1 1 1 6 (B-4) MMA 5 5 5 BA 5 5 5 Average particle size of 0.25 0.25 0.13 0.25 rubber particles (m)

Production Example 5

Production of Rubber-Containing Graft Copolymer (C1)

(31) The following substances were charged into an 8-liter polymerization apparatus equipped with a stirrer.

(32) TABLE-US-00003 Deionized water 200 parts Sodium dioctyl sulfosuccinate 0.25 parts Sodium formaldehyde sulfoxylate 0.15 parts Disodium ethylenediaminetetraacetate 0.001 parts Ferrous sulfate 0.00025 parts

(33) Air was fully purged from the polymerization apparatus with nitrogen gas so that the polymerization apparatus contained substantially no oxygen. Then, the temperature in the polymerization apparatus was set to 60 C., and a mixed liquid of a monomer mixture composed of 27 parts of n-butyl acrylate, 3 parts of methyl methacrylate, and 0.9 parts of allyl methacrylate and 0.2 parts of cumene hydroperoxide was continuously added over 3 hours. After the completion of the addition, polymerization was further continued for 0.5 hours to obtain rubber particles (which were a polymerization product of (C-1)). The polymerization conversion rate of the rubber particles was 99.5%.

(34) Then, 0.05 parts of sodium dioctyl sulfosuccinate was charged, and then the temperature in the polymerization apparatus was set to 60 C., a mixed liquid of a monomer mixture composed of 7 parts of n-butyl acrylate and 63 parts of methyl methacrylate and 0.2 parts of cumene hydroperoxide was continuously added over 5 hours, and polymerization was further continued for 1 hour to obtain a rubber-containing graft copolymer latex. The polymerization conversion rate of the rubber-containing graft copolymer latex was 98.5%. The obtained latex was subjected to salting-out and coagulation with calcium chloride, washing with water, and drying to obtain a white powder of a rubber-containing graft copolymer (C1).

(35) The average particle size of rubber particles of the rubber-containing graft copolymer (C1) was 0.08 m.

Examples 1 to 7 and Comparative Examples 1 to 5

(36) The obtained powdery rubber-containing graft copolymers (B) and (C) were blended to achieve their respective numbers of parts of rubber particles shown in Table 3, and the rubber-containing graft copolymers (B) and (C) and SUMIPEX EX (which is a methacrylate-based resin containing 95 wt % of methyl methacrylate and 5 wt % of methyl acrylate manufactured by Sumitomo Chemical Company, Limited) were blended so that their total amount was 100 parts with a blending machine (SUPERFLOATER SFC-50 manufactured by KAWATA MFG Co., Ltd.) for 3 minutes and then melt-kneaded using a 40 mm single screw extruder equipped with a vent at a cylinder temperature of 240 C. to obtain pellets. The obtained pellets were molded using a 40 mm extruder equipped with a T die (NEX040397 manufactured by Nakamura Sanki K.K.) at a die temperature of 240 C. to obtain a 100 m-thick film.

(37) Various properties of the obtained film using the powders were evaluated and the results of the evaluations are shown in Table 2. It is to be noted that the number of parts of rubber particles shown in Table 2 is the number of parts by weight per 100 parts by weight of a whole resin composition.

(38) TABLE-US-00004 TABLE 2 Examples Comparative Examples 1 2 3 4 5 6 7 1 2 3 4 5 Rubber-containing graft copolymer (B) B1 B1 B1 B1 B1 B1 B1 B2 B3 B4 B2 Rubber-containing graft copolymer (C) C1 C1 C1 C1 C1 C1 C1 C1 C1 C1 C1 Number of Rubber-containing 5 5 10 5 3.1 1.9 3.8 5 0 5 5 10 parts of rubber graft copolymer (B) particles (parts) Rubber-containing 15 30 10 5 34.5 28.5 21.2 15 20 10 15 0 graft copolymer (C) Cracking resistance A A A A A A A A B B A A Pencil hardness H F H 2H H H H F F H H H Resistance to whitening on bending A A A A A A A A A A A C Haze 0.6 0.7 0.7 0.5 0.5 0.5 0.5 1.3 0.5 0.5 1.5 1.8

Examples 8 to 13 and Comparative Examples 5 to 8

(39) A urethane acrylate-based resin dispersion liquid containing RC29-124 (manufactured by DIC Corporation) and having a solid content concentration of 30% was applied onto each of the films obtained in Examples 5 to 7 and Comparative Examples 1 to 3 and 5 with a bar coater (#6 or #10). After the completion of the coating operation, the film was dried at 80 C. for 1 min to volatilize a solvent and then irradiated with ultraviolet rays at 748.4 mJ/min to form a coating layer having a thickness of 4 m or 7 m. Various properties of the obtained film were evaluated and the results of the evaluations are shown in Table 3.

(40) TABLE-US-00005 TABLE 3 Examples Comparative Examples 8 9 10 11 12 13 5 6 7 8 Base film Example Example Example Example Example Example Comparative Comparative Comparative Comparative 5 5 6 6 7 7 Example 1 Example 2 Example 3 Example 5 Film thickness of 4 7 4 7 4 7 4 4 4 4 coating layer (m) Cracking resistance A B A B A B A C B A Pencil hardness H H 2H 2H 2H 2H F F 2H 2H Resistance to A A A A A A A A A C whitening on bending Haze 0.4 0.4 0.3 0.4 0.3 0.3 1.3 0.5 0.5 1.5 Tensile elongation 30 20 30 20 30 20 30 30 30 30 at 120 C. (%)