JPH0721095B2 - Acrylic resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an acrylic resin composition containing a sulfonic acid metal salt having a specific structure and an inorganic filler, and having excellent light scattering properties and stress crack resistance. .

2. Description of the Related Art Acrylic resins are used in various applications because of their excellent optical properties, good mechanical properties, processing properties, and appearance. Among them, milk white acrylic resin in which an inorganic filler is dispersed in a resin to give a light scattering property is used for applications such as a lamp cover of a lighting fixture and a signboard. In these applications, a molded article obtained by secondary molding of a light-scattering acrylic resin sheet by press molding, vacuum molding, or the like,
A molded product obtained by injection molding a light-scattering acrylic resin is used.

Molded products of a light-scattering acrylic resin are required to have contradictory properties of low linear light transmittance and high total light transmittance. Therefore, in order to adjust the balance between the linear light transmittance and the total light transmittance, an acrylic resin as a base material is selected by selecting the particle size and the addition amount of the inorganic filler having a different refractive index from the acrylic resin. Heretofore, various light-scattering acrylic resin compositions dispersed in various types have been proposed.

For example, JP-A-51-56851 discloses a neodymium compound,
Japanese Unexamined Patent Publication No. 53-147748 discloses talc, Japanese Unexamined Patent Publication No. 57-5742 discloses silicon dioxide, Japanese Unexamined Patent Publication No. 59-16551 discloses calcium carbonate, and Japanese Unexamined Patent Publication No. 61-78859 discloses. There is proposed an acrylic resin in which an inorganic filler such as talc, silicon dioxide, barium sulfate, or calcium carbonate is added to impart light scattering property.

However, the acrylic resin blended with the inorganic filler has a higher residual stress inside the molded product due to the orientation of the inorganic filler during molding, resulting in lower stress crack resistance to solvents than the unblended acrylic resin. It has the drawback of If the stress crack resistance to the solvent is poor, there are disadvantages that cracks easily occur due to contact with a solvent such as alcohol, or cracks easily occur due to a coating process or spraying with an insecticide or the like.

As a method for improving the stress crack resistance of the acrylic resin, an annealing treatment is usually performed by leaving it in an air bath at a temperature slightly lower than the heat distortion temperature of the acrylic resin for 1 to 3 hours after molding. There is. Further, in some cases, this alone is not sufficient, and a portion of the molded product where stress cracking is likely to occur is provided with a thickness, or the portion is designed into a curved surface to improve the stress crack resistance. However, these methods have the drawback that the shape of the molded product is limited.

Therefore, in the production process, the complicated annealing treatment can be omitted or the treatment time can be shortened, which is advantageous in designing the shape of the molded product, and the acrylic resin with improved stress crack resistance has not been obtained at present. is there.

In addition, when the milky acrylic resin composition containing an inorganic filler is molded, there is a problem that color unevenness is likely to occur in each molded product.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide an acrylic resin composition having improved stress crack resistance and light scattering.

Another object of the present invention is to prevent the occurrence of color unevenness for each molded product.

As a result of intensive studies on the above problems, the present inventors have used a sulfonic acid metal salt having a specific structure and an inorganic filler in combination to improve the stress crack resistance and light scattering resistance of the acrylic resin. It has been found that a composition is obtained.

That is, the acrylic resin composition of the present invention comprises a sulfonic acid metal salt (A) represented by the following general formula (I) or (II) and an inorganic filler (B) in a weight ratio of the acrylic resin. Is (A) / (B) = 25/75 to 75/25, and
The total amount [(A) + (B)] of both is compounded in the range of 1.0 to 6.0% by weight.

R-SO ₃ M (I) (However, R: C _{8 to} C ₂₂ straight-chain or branched long-chain alkyl group or alkenyl group M: alkali metal or alkaline earth metal) The present inventors also described above (A), (B ) It has been found that color unevenness of each molded product can be eliminated by adding a higher alcohol in addition to both components.

Hereinafter, the present invention will be described in more detail.

As the acrylic resin used in the present invention, a methyl methacrylate homopolymer or a copolymer containing 70% by weight or more of methyl methacrylate is suitable. Examples of this copolymer include copolymers with acrylic acid esters, methacrylic acid esters other than methyl esters, acrylic acid, methacrylic acid, styrene, acrylonitrile and the like. Examples of the acrylate ester include methyl acrylate,
Ethyl acrylate, butyl acrylate and the like, and examples of the methacrylic acid ester include cyclohexyl methacrylate and the like.

The molecular weight of the above polymer or copolymer is 50,000 to 500,000
Is preferred, and is preferably 70,000 to 300,000.

Specific examples of the sulfonic acid metal salt represented by the general formula (I) of the present invention include sodium octyl sulfonate, lithium octyl sulfonate, potassium octyl sulfonate, sodium isooctyl sulfonate, sodium octadecyl sulfonate, nonyl sulfonic acid. Examples thereof include soda, sodium decyl sulfonate, sodium dodecyl sulfonate, and lithium decyl sulfonate. Also, the average carbon number of the alkyl group is
It is also possible to use 13 to 16 paraffin sulfonic acid metal salts and α-olefin sulfonates.

Examples of the sulfonic acid metal salt represented by the general formula (II) include, for example, sodium isooctylbenzenesulfonate, sodium octadecylbenzenesulfonate, sodium isooctadecylbenzenesulfonate, potassium octylbenzenesulfonate, sodium nonylbenzenesulfonate, and dodecyl. Examples thereof include sodium benzenesulfonate.

In the present invention, when the chain length of the long-chain alkyl group of the sulfonic acid metal salt represented by the general formula (I) or (II) is shorter than C ₈ , the surface of the acrylic resin molded article becomes sticky. Inappropriate. Also, if it is longer than C ₂₂ , it is economically disadvantageous.

Examples of the inorganic filler which is the component (B) of the present invention include barium sulfate, titanium oxide, talc, magnesium silicate, calcium carbonate, silicon dioxide, aluminum hydroxide, neodymium phosphate, calcium sulfate, titanium dioxide, calcium fluoride. Known substances as a light-scattering agent for acrylic resins, such as sodium aluminosilicate, aluminum silicate, zinc oxide and calcium silicate are used. These fillers may be used in combination of two or more.

The type and particle size of these inorganic fillers are determined by the surface smoothness, light transmittance, and light scattering properties required for the molded product, but the inorganic fillers with a particle size of about 0.5 to 20μ, preferably 0.5 to 10μ. Is desirable.

The stress crack resistance of the light-scattering acrylic resin molded product to which the above-mentioned inorganic filler is added alone is lower than that of the molded product of the resin not added, contact with a solvent such as alcohol, an insecticide, etc. It is practically disadvantageous that cracks are easily generated by spraying of.

In the present invention, the combined ratio of the sulfonic acid metal salt (A) represented by the general formula (I) or (II) and the inorganic filler (B) is
Weight ratio (A) / (B) = 25/75 to 75/25, preferably 30
The range is / 70 to 70/30.

When it is in this range, the stress crack resistance is good, and the linear light transmittance is reduced and the light scattering property is improved as compared with the light scattering acrylic resin to which the inorganic filler is added alone. . Further, as compared with the case of using it alone, the compounding amount of the inorganic filler necessary for achieving the desired linear light transmittance can be reduced, and the total light transmittance can be improved.

If the ratio of the component of the sulfonic acid metal salt (A) is larger than this range, the surface of the molded article tends to be sticky, which is disadvantageous. When the ratio of the component (B) is larger than this range, the stress crack resistance is not improved and the linear light transmittance is not lowered.

The total amount of the sulfonic acid metal salt (A) and the inorganic filler (B) blended into the acrylic resin is 1.0 to 6.0% by weight, and the blending amount is the thickness and surface required for the target molded article. Determined by smoothness, light transmittance, and light scattering. Generally, the linear light transmittance of the light-scattering acrylic resin is required to be 10% or less, although it depends on the application.

When the total amount of both components (A) + (B) is less than 1.0% by weight, the transmittance of linear light rays does not decrease even when both components are used together, and in applications where light diffusivity is required. Is insufficient. On the other hand, when the total content (A) + (B) exceeds 6.0% by weight, the total light transmittance of the molded product is lowered and the transparency is impaired, which is disadvantageous in the application of a lighting fixture cover. .

Furthermore, by combining a higher alcohol (C) in addition to the sulfonic acid metal salt (A) and the inorganic filler (B), it is possible to eliminate color unevenness in each molded product.

Carbon chain length of the higher alcohol (C) is suitably C ₈ -C _22, preferably a C ₁₂ -C _18.

Specific examples of such higher alcohols include, for example,
2-ethylhexyl alcohol, octyl alcohol,
Dodecyl alcohol, octadecyl alcohol, oleyl alcohol, eicosanol, docosanol and the like can be mentioned.

The amount of the higher alcohol (C) added is (C) / (A) = 10/90 to 40/60 in terms of weight ratio with the sulfonic acid metal salt (A).
Is preferred. If the mixing ratio is less than 10/90, the prevention of color unevenness is insufficient. On the other hand, if it exceeds 40/60, it is possible to prevent the occurrence of color unevenness, but it is not preferable because the surface of the molded product tends to become sticky.

The composition of the present invention can be obtained by a usual kneading operation of an acrylic resin. For example, it can be obtained by dry blending an acrylic resin, the sulfonic acid metal salt (A) and the light-scattering inorganic filler (B) with a mixer such as a Henschel mixer or a tumbler, and then melt-kneading with an extruder.

It can also be obtained by previously kneading the sulfonic acid metal salt (A) in a high concentration in an acrylic resin to form a masterbatch, and blending the master batch with the light-scattering inorganic filler into the acrylic resin. It is also possible to dilute the masterbatch with an acrylic resin in which an inorganic filler has been kneaded in advance and mold it. Further, it can also be obtained by adding the above-mentioned sulfonic acid metal salt (A) to a raw material monomer, polymerizing it, and kneading it with an inorganic filler.

When the higher alcohol (C) of the present invention is added, it is possible to mix it alone with the sulfonic acid metal salt (A) and the inorganic filler (B) in the acrylic resin, and the sulfonic acid metal salt (A) may be added in advance. It is also possible to add what was melt-mixed with this).

Other additives can be added to the acrylic resin composition of the present invention as needed. For example, oxazole-based and coumarin-based fluorescent agents, phosphorus-based antioxidants such as trisalkylphenylphosphite, sulfur-based antioxidants such as dilauryl 3,3-thiopropionate, and phenol-based antioxidants such as butylated hydroxytoluene Agents, ultraviolet absorbers, antistatic agents, or lubricants such as ethylene bisamide, monoalkyl amide, and fatty acid monoglyceride. It is also possible to use a coloring agent such as a bluing agent.

The composition obtained by the present invention can be molded by a usual molding method applied to an acrylic resin, injection molding,
It is possible to apply a forming method such as vacuum forming and pressure forming after forming into a sheet with an extruder.

The molded article of the composition obtained by the present invention can be applied to various shapes such as lighting fixtures, electric meters, covers and parts for electronic devices, meter covers, films, sheets, panels and the like.

EFFECTS OF THE INVENTION According to the present invention, an acrylic resin having excellent stress crack resistance and improved light scattering can be obtained by using a specific sulfonate and an inorganic filler in combination. Although the mechanism is not clear, stress crack resistance is improved because the sulfonate has the effect of relaxing the residual stress caused by the orientation of the inorganic filler during molding in the acrylic resin. It is considered to be a thing. Furthermore, it is considered that the metal sulfonate has an effect of affecting the dispersion state of the inorganic filler, reducing the linear light transmittance and improving the light scattering property.

Furthermore, by mixing together the higher alcohol (C) in addition to the sulfonic acid metal salt (A) and the inorganic filler (B) described above, it is possible to eliminate the occurrence of color unevenness in each molded product.

Although the mechanism of this action is not clear, it is considered that the dispersibility of the inorganic filler (B) is further improved by the synergistic effect of the sulfonic acid metal salt (A) and the higher alcohol (C).

Hereinafter, the present invention will be described in detail with reference to examples.

Examples 1 to 18 and Comparative Examples 1 to 24 Methacrylic resin (Mitsubishi Rayon Co., Ltd., acrylic PET VH), sulfonic acid metal salt represented by the general formula (I) or (II) and inorganic filler are shown in Table 1. Premixed in a Henschel mixer at the indicated proportions.

This mixture was melt-kneaded at 250 ° C using a vented twin-screw extruder, and the resulting strand was cut with a pelletizer and pelletized, then injection-molded at 260 ° C with an injection molding machine to obtain 100 x 100 x 1.5 mm. Sheet (test piece A) and a test piece (test piece B) having the shape shown in FIG. 1 were obtained. Using these test pieces, the following items were evaluated.
No annealing treatment was performed after injection molding.

Hereinafter, an acrylic resin (Mitsubishi Rayon Co., Ltd., acrylic PET VH), a sulfonic acid metal salt represented by the general formula (I) or (II), and an inorganic filler were blended in the proportions shown in Tables 2 and 3,
A comparative composition was obtained according to the method of the above example, and evaluated in the same manner as in the example.

The above results are summarized in Tables 1 to 3 below.

Total light transmittance and linear light transmittance Total light transmittance and linear light transmittance were measured by an integrating sphere type HTR meter according to ASTM D-1003. Total light transmittance of 60
% Or more is acceptable, and linear light transmittance is 10% or less.

Stress crack resistance Test piece B is immersed in ethanol, dried at room temperature, fixed in a mold (see Fig. 2), and subjected to a heat cycle test of 10 hours under an atmosphere of 80 ° C for 1 hour and under an atmosphere of room temperature for 10 cycles. Then, it was evaluated at what cycle the crack occurred.

Surface condition The surface condition of the test piece A was judged by touch.

Good ... not sticky Bad ... sticky Examples 19 to 24, Reference Examples 1 to 2 Methacrylic resin (Mitsubishi Rayon Co., Ltd., Acrylic PET VH), sodium paraffin sulfonate, inorganic filler and higher alcohol in the proportions shown in Table 4 were preliminarily used in a Henschel mixer. After mixing and kneading in the same manner as in Examples 1 to 18 and injection molding, test pieces A and B were obtained in the same manner.

For these test pieces, total light transmittance, measurement of linear light transmittance, determination of surface state, stress crack resistance test is performed in the same manner as in Examples 1 to 18, and the color unevenness determination test is described below. It carried out by the method shown. Example 25 to be described later
The results are shown in Table 5 together with 28.

Color unevenness determination test Twenty test pieces A were randomly sampled and the number of test pieces with color unevenness was counted. The number of test pieces having color unevenness is 5 or less, and the result is acceptable.

Examples 25 to 28, Reference Examples 3 to 4 Methacrylic resin (Mitsubishi Rayon Co., Ltd., Acrylic PET VH), sodium paraffin sulfonate, inorganic filler and higher alcohol were added in a Henschel mixer at the ratios shown in Table 4. They were mixed and kneaded in the same manner as in Examples 1-18. The pellets obtained are then packed in a vented extruder 13
It was extruded into a plate with a width of 00 mm and a thickness of 1.5 mm. The obtained acrylic plate was cut into a sheet of 100 × 100 × 1.5 mm to obtain a test piece (test piece C).

Further, the obtained acrylic plate was formed by vacuum forming to obtain a test piece (test piece D) shown in FIG.

For the test piece C, the total light transmittance, the linear light transmittance were measured, the surface condition was judged, and the color unevenness was judged in Examples 19 to 24.
Evaluation is carried out in the same manner as in Example 19 to 24 for the test piece D.
The stress crack resistance test was evaluated in the same manner as in. The results are shown in Table 5.

[Brief description of drawings]

FIG. 1 is a perspective view showing the shape and dimensions of the test piece B used in the examples. FIG. 2 is a side view showing a method of fixing the test piece B in the evaluation test of the example. FIG. 3 is a perspective view showing the shape and dimensions of the test piece D used in the examples. 11 ... Test piece B, 13 ... Mold 15 ... Screw, 17 ... Test piece D

Claims (3)

[Claims] 1. An acrylic resin containing a sulfonic acid metal salt (A) represented by the following general formula (I) or (II) and an inorganic filler (B) in a weight ratio of (A) / (B). ) = 25/75 ~ 7
5/25 and total amount of both [(A) + (B)]
Is compounded in the range of 1.0 to 6.0% by weight, the acrylic resin composition. R-SO ₃ M (I) (However, R: C _{8 to} C ₂₂ straight-chain or branched long-chain alkyl group or alkenyl group M: alkali metal or alkaline earth metal) 2. The acrylic resin composition according to claim 1, which further contains a higher alcohol (C). 3. The acrylic according to claim 2, wherein the higher alcohol (C) has 8 to 22 carbon atoms, and the weight ratio is (C) / (A) = 10/90 to 40/60. -Based resin composition.