JPH04198248A - Acrylic resin composition - Google Patents

Abstract

PURPOSE:To improve light-scattering properties and resistance to stress crack by compounding an acrylic resin, a specific metal sulfonate, an inorg. filler, and an aliph. alcohol ester of a higher fatty acid. CONSTITUTION:An acrylic resin having a mol.wt. of 50000-500000 and contg. 70wt.% or higher methyl methacrylate units, 1.0-6.0wt.% the sum of 25-75wt.% metal sulfonate of formula I or II (wherein R is 8-22C linear or branched long- chain alkyl or alkenyl; and M is an alkali or alkaline earth metal) and 75-25wt.% inorg. filler having a particle size of 0.5-20mum (e.g. BaSO4, and an ester of a 1-22C aliph. alcohol with an 8-18C higher fatty acid in a wt. ratio of the ester to the resin of (10:90)-(40:60) are compounded.

Description

Detailed Description of the Invention The present invention contains a sulfonic acid metal salt, an inorganic filler, and a higher fatty acid ester, and has excellent light scattering properties and stress crack resistance. The present invention relates to an acrylic resin composition in which color unevenness is prevented from occurring.

Acrylic resins are used in a variety of applications due to their excellent optical properties, good mechanical properties, processing properties, and appearance. Among these, milky white acrylic resins, which have light scattering properties by dispersing inorganic fillers in the resin, are used for applications such as lamp covers for lighting equipment and signboards. In these applications, molded products obtained by secondary forming sheets of light-scattering acrylic resin by press molding, vacuum forming, etc.
A molded article obtained by injection molding a light-scattering acrylic resin is used.

Molded articles made of light-scattering acrylic resin are required to have contradictory properties: low linear light transmittance and high total light transmittance. Therefore, in order to adjust the balance between linear light transmittance and total light transmittance, we selected an inorganic filler with a different refractive index from that of the acrylic resin in terms of particle size and amount added to the base acrylic resin. Various light-scattering acrylic resin compositions have been proposed in the past.

For example, JP-A-51-56851 discloses a neodymium compound, JP-A-53-147748 discloses talc, JP-A-57-5742 discloses silicon dioxide, and JP-A-59-16551 discloses a neodymium compound. JP-A-61-78859 proposes an acrylic resin blended with inorganic fillers such as talc, silicon dioxide, barium sulfate, and calcium carbonate to impart light scattering properties.

However, in acrylic resins containing inorganic fillers, the inorganic fillers become oriented during molding, increasing residual stress inside the molded product, resulting in lower stress crack resistance to solvents than acrylic resins without inorganic fillers. It has the following drawbacks. If the stress crack resistance against solvents is poor, cracks may easily occur due to contact with solvents such as alcohol, or cracks may easily occur during painting processes or spraying with insecticides.

As a method to improve the stress crack resistance of acrylic resin, it is usual to perform an annealing treatment 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. In some cases, this alone is not sufficient, so attempts are being made to increase the thickness of the parts of the molded product where stress cracks are likely to occur, or to design those parts to have curved surfaces to improve stress crack resistance. However, these methods have the disadvantage that the shape of the molded product is limited.

Therefore, it is currently not possible to obtain an acrylic resin with improved stress crack resistance, which is advantageous in designing molded product shapes and can omit complicated annealing treatment or shorten processing time in the production process. be.

The present inventors first achieved stress resistance of the acrylic resin composition by blending the sulfonic acid metal salt (A) of the present invention and the filler (B) in a specific weight ratio and total amount of the acrylic resin. It has been found that cracking properties and light scattering properties are improved (Japanese Patent Application No. 100778/1999). Furthermore, when an acrylic resin composition made milky white by adding an inorganic filler is molded in this way, there is a problem in that color unevenness tends to occur in each molded product.

The object of the present invention is to improve the stress crack resistance and light scattering properties of an acrylic resin composition, and to prevent the occurrence of color unevenness in each molded product.

The acrylic resin composition of the present invention includes acrylic resin,
The following components (A), (B), and (C) are blended, and the blending weight ratio of sulfonic acid metal salt (A) and inorganic filler (B) is (A)/(B) = 25/75 ~ 75/25, and the total amount of both [(A)+(B)] is 1.0 to 6.0% by weight.

(A): A sulfonic acid metal salt represented by the following general formula (I) or (TJ).

R-SO3M...(I) (R: C, ~ C1, linear or branched long chain alkyl group or alkenyl group M: alkali metal or alkaline earth metal) (B): Inorganic filling agent.

(C): Ester of higher fatty acid and aliphatic alcohol.

The present invention will be explained in more detail below.

As the acrylic resin used in the present invention, methyl methacrylate homopolymer or methyl methacrylate
Copolymers containing at least % by weight are preferred. Examples of this copolymer include copolymers with acrylic esters, methacrylic esters other than methyl esters, acrylic acid, methacrylic acid, styrene, acrylonitrile, and the like.

Examples of acrylic esters include methyl acrylate, ethyl acrylate, butyl acrylate, and examples of methacrylic esters include cyclohexyl methacrylate.

The molecular weight of the above polymer or copolymer is 50,000~s
oo, ooo are suitable, preferably 70.000
~300,000.

Specific examples of the sulfonic acid metal salt represented by the general formula (I) of the present invention include sodium octylsulfonate, lithium octylsulfonate, potassium octylsulfonate, sodium isooctylsulfonate, sodium octadecylsulfonate, and nonylsulfonic acid. Examples include soda, sodium decylsulfonate, sodium dodecylsulfonate, lithium decylsulfonate, and the like. It is also possible to use paraffin sulfonic acid metal salts and α-olefin sulfonate salts in which the average number of carbon atoms in the alkyl group is 13 to I6.

As the sulfonic acid metal salt represented by general formula (II),
Examples include sodium isooctylbenzenesulfonate, sodium octadecylbenzenesulfonate, sodium isooctadecylbenzenesulfonate, potassium octylbenzenesulfonate, sodium nonylbenzenesulfonate, and sodium dodecylbenzenesulfonate.

In the present invention, the chain length of the long chain alkyl group of the sulfonic acid metal salt represented by general formula (I) or (II) is C,
If it is shorter than this, it is inappropriate because the surface of the acrylic resin molded product will become sticky.

Moreover, if it is longer than C3, it is economically disadvantageous.

Inorganic fillers that are 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, and calcium fluoride. , sodium aluminosilicate, aluminum silicate, zinc oxide, calcium silicate, and other known light scattering agents for acrylic resins are used. Two or more types of these fillers can also be used in combination.

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 are approximately 0.5 to 20μ, preferably 0.5 to 10μ.
Inorganic fillers with a particle size of μ are preferred.

The stress cracking resistance of light-scattering acrylic resin molded products to which the above-mentioned inorganic filler is added alone is lower than that of molded products made of resin to which no inorganic filler is added, and is susceptible to contact with solvents such as alcohol, insecticides, etc. This is disadvantageous in practical terms, as cracks easily occur when sprayed.

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 from (A)/(B) = 25/75 by weight. 75/
25, preferably in the range of 30/70 to 70/30.

If it is within this range, the crucian carp stress cracking resistance is good, and compared to a light-scattering acrylic resin containing only an inorganic filler, the straight light transmittance is lower and the light-scattering property is improved. . Furthermore, compared to the case where the inorganic filler is used alone, the amount of inorganic filler required to achieve the desired straight light transmittance can be reduced, and it is also possible to improve the total light transmittance.

If the ratio of the component of the sulfonic acid metal salt (A) is more than the above range, it is disadvantageous because the surface of the molded product tends to become sticky. On the other hand, if the ratio of the inorganic filler (B) is greater than the above range, the stress crack resistance will not be improved and the straight light transmittance will not decrease.

The total blending amount of the sulfonic acid metal salt (A) and the inorganic filler (B) in the acrylic resin is 1.0 to 6.0% by weight, but the blending amount is determined according to the amount necessary for the intended molded product. Determined by thickness, surface smoothness, light transmittance, and light scattering properties. Generally, the straight light transmittance of the light-scattering acrylic resin is required to be 10% or less, although it varies depending on the application.

Total blending amount of both components (A) + (B) is 1.0% by weight
If it is less than 1, the transmittance of straight light does not decrease even if both components are used together, and it is insufficient for applications that require light diffusivity. On the other hand, if the total blending amount (A) + (B) exceeds 6.0% by weight, the total light transmittance of the molded product will decrease and the transparency will be impaired, which is disadvantageous when used as a lighting equipment cover. It is.

In the present invention, an ester of a higher fatty acid and an aliphatic alcohol is blended as the component (C), thereby preventing the occurrence of color unevenness in each molded product.

The carbon chain length of the higher fatty acid moiety of ester (C) is C0~
Cl m is preferred, more preferably C3, ~C1
, is. Further, the carbon chain length of the aliphatic alcohol moiety of the ester (C) is preferably C1 to Cj j, more preferably C1 to C1.

Specific examples of the ester (C) include methyl octadecenoate, ethyl octadecenoate, butyl octadecenoate, hexyl octadecylate, butyl isooctadecylate, methyl octadecenoate, ethyl octadecenoate,
Examples include butyl hexadecylate and butyl dodecylate.

In addition, the amount of ester (C) added is determined by the amount of sulfonic acid metal salt (
Weight ratio with A) (C) / (A) = 10/90
A range of 40/60 is preferred. This blending ratio is 107
If it is less than 90, 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 the surface of the molded product tends to become sticky, which is not preferable.

The composition of the present invention can be obtained by a conventional acrylic resin kneading operation. For example, acrylic resin, sulfonic acid metal salt (A), inorganic filler (B) and ester (
C) is triblended using a mixer such as a Henschel mixer or a tumbler, and then melt-kneaded using an extruder.

The above sulfonic acid metal salt (A) and ester (C) in advance
It can also be obtained by kneading it into an acrylic resin at a high concentration to make a masterbatch, and blending it into the acrylic resin together with a light-scattering inorganic filler. Moreover, it is also possible to dilute the masterbatch with an acrylic resin into which an inorganic filler has been kneaded in advance and to form the masterbatch. Furthermore, it can also be obtained by adding the above-mentioned sulfonic acid metal salt (A) and ester (C) to a raw material, polymerizing it, and kneading it with an inorganic filler. It is also possible to melt and mix the ester (C) with the sulfonic acid metal salt (A) in advance and add the mixture to the acrylic resin.

Other additives can be added to the acrylic resin composition of the present invention as necessary. For example, oxazole-based and coumarin-based fluorescent agents, phosphorus-based antioxidants such as trisalkylphenyl phosphite, sulfur-based antioxidants such as dilauryl 3,3-thiopropionate, and phenolic antioxidants such as butylated hydroxytoluene. agent, ultraviolet absorber, antistatic agent, or lubricant such as ethylene bisamide, monoalkyl amide, fatty acid monoglyceride,
2-ethylhexyl alcohol, octyl alcohol,
C1 such as dodecyl alcohol, octadecyl alcohol, oleyl alcohol, eicosanol, docosanol, etc.
- Cs t higher alcohols.

It is also possible to use colorants such as bluing agents.

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

Molded articles of the composition obtained by the present invention can be applied to various shapes such as lighting equipment, electrical meters, covers and parts for electronic devices, meter covers, films, sheets, and panels.

According to the present invention, by combining a specific sulfonic acid metal salt, an inorganic filler, and an ester, excellent stress crack resistance and improved light scattering properties are achieved, and the moldability is improved. Acrylic resin can be obtained in which color unevenness is prevented from occurring from product to product. Although the mechanism is not clear, the sulfonic acid metal salt has the effect of alleviating the residual stress that occurs due to the orientation of the inorganic filler within the acrylic resin during molding, resulting in improved stress cracking resistance. It is considered that Furthermore, the sulfonic acid metal salt is considered to have the effect of affecting the dispersion state of the inorganic filler, lowering the straight light transmittance, and improving the light scattering property.

In addition, it is thought that the dispersibility of the inorganic filler (B) is further improved due to the synergistic effect of the sulfonic acid metal salt (A) and the ester (C), so that the occurrence of color unevenness can be eliminated.

Hereinafter, the present invention will be explained in detail with reference to Examples.

-]~8゛ and 12 Methacrylic resin (Clary ■, Parapet G), sulfonic acid metal salt (A), inorganic filler (B) and ester (
C) were premixed in the proportions shown in Table 1 in a Henschel mixer. However, in Comparative Example 1, ester (C) was not added.

This mixture was melt-kneaded at 250°C using a vented twin-screw extruder, the resulting strands were cut into pellets using a pelletizer, and then heated to 260°C using an injection molding machine.
A sheet (test piece A) of +00 x 100 x 1.5 mm and a test piece (test piece B) having the shape shown in FIG. 1 were obtained by injection molding. No annealing treatment was performed after injection molding.

Regarding these test pieces, total light transmittance and straight light transmittance were measured by the following method, and stress resistance, surface condition, and color unevenness were evaluated.

The above results are shown in Table 1 (composition of acrylic resin composition) and Table 2 (
Measurement and evaluation results).

゛・ and ′0 Total light transmittance and straight light transmittance as per ASTM D-1
It was measured using an integrating sphere type (ITR) meter according to 003.

The total light transmittance is 60% or more, and the straight light transmittance is 1.
0% or less is a pass.

After immersing the stress crack test piece B in ethanol, it was dried at room temperature, fixed in a mold (see Figure 2), and subjected to an IO cycle test of 1 hour in an 80"C atmosphere and 1 hour in a room temperature atmosphere. It was evaluated whether cracks would occur in the 1st cycle.

11 thick plates The surface condition of test piece A was determined by touch.

Good: Not sticky Poor: Sticky L work 20 narrow test pieces A were randomly sampled, and the number of test pieces with uneven color was counted.

If the number of test pieces with uneven coloring is 5 or less, it is considered to be a pass.

-9 to LLJ and 13 Methacrylic resin (Clary ■, Paravet G), sulfonic acid metal salt (A), inorganic filler (B) and ester (
C) were premixed in a Henschel mixer in the proportions shown in Table 1, and kneaded in the same manner as in Examples 1-8. The resulting pellet was molded into a 1300mm extruder using a vented extruder.
It was extruded into a plate shape with a width of 1.5 mm and a thickness of 5 mm.

The obtained acrylic board was 100 x 100 x 1.5
A test piece (test piece C) was obtained by cutting into a sheet of mm.

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

Measurement of total light transmittance, straight light transmittance, surface condition determination, and color unevenness determination test were performed on test piece C, and stress crack resistance tests were conducted using the test piece in the same manner as in Examples 1 to 9. I did it. The above results are shown in Tables 1 and 2.

(Margin below)

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the shape and dimensions of test piece B used in Examples. FIG. 2 is a side view showing a method of fixing test piece B in the evaluation test in the example. FIG. 3 is a perspective view showing the shape and dimensions of the test piece used in the example.

Claims (1)

[Claims] 1. The following general formula (I) or (II) is added to the acrylic resin.
) and the inorganic filler (B) in a weight ratio of (A)/(B)=25/75.
~75/25, and the total amount of both [(A)+
(B)] in a range of 1.0 to 6.0% by weight, and further contains an ester (C) of a higher fatty acid and an aliphatic alcohol. R-SO_3M...(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(II) (However, R: C_8 to C_2_2 linear or branched long-chain alkyl group or alkenyl group M: 2. Ester of higher fatty acid and aliphatic alcohol (C)
The higher fatty acid has 8 to 18 carbon atoms, the aliphatic alcohol has 1 to 22 carbon atoms, and the weight ratio is (C)
The acrylic resin composition according to claim 1, wherein /(A) is in the range of 10/90 to 40/60.