JPS5910745B2 - Solvent resistant acrylic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improved thermoplastic acrylic resin compositions.

More specifically, the present invention relates to a thermoplastic acrylic resin composition with improved solvent resistance. Acrylic resin is widely used both indoors and outdoors due to its excellent transparency, weather resistance, beautiful appearance, and ease of molding.

However, when it comes into contact with certain solvents, glazes and cracks may occur, especially when internal stress or external stress is applied, and improvements have been desired. Conventionally, methods for improving solvent resistance have been proposed, for example, by incorporating acrylic or methacrylic oligomers (Japanese Patent Laid-Open No. 49-13
1241) and a method of copolymerizing certain acrylic and methacrylic monomers (Japanese Patent Application Laid-open No. 53-JMo V92 and Japanese Patent Application Laid-Open No. 54-99190).

Regarding multilayer structure polymers, for example,
No. 27,576 shows that blends of trilayer or multilayer polymers and rigid thermoplastic polymers improve impact resistance without sacrificing transparency. It is explained that the desirable particle size in this case is 1,600 to 2,800 particles. In addition, polymers with a complex structure of five or more layers (hard, soft, and hard) and an intermediate layer with a taper between each layer (
JP-A-51-129449 and JP-A-53-15855
4), or a polymer consisting of a four-layer structure of one soft, one hard, and one soft and hard (Japanese Patent Application Laid-Open No. 94917) has been proposed as an impact resistance modifier with excellent stress whitening resistance. There is.
As a result of extensive research into improving the solvent resistance of acrylic resins, the present inventors discovered a method for improving the solvent resistance of acrylic resins without impairing their transparency, weather resistance, and processability. I was able to complete it.

That is, the solvent-resistant acrylic resin composition of the present invention contains (4) methyl methacrylate alone or together with 20% by weight or less of an alkyl group having 1 to 8 carbon atoms when the total weight is 100 parts by weight. 20 to 98 parts by weight of a hard thermoplastic acrylic resin obtained by polymerizing at least one alkyl acrylate, 20% by weight or less of a monomer copolymerizable with these, or a monomer mixture consisting of both; ) 2 to 80 parts by weight of a three-layer structure polymer, and the three-layer structure polymer is (1) 55 to 80 parts by weight.
99.9% by weight methyl methacrylate and 0.1-5
% by weight of polyfunctional grafting agent, or with 20
Polymerizing at least one alkyl acrylate whose alkylene group has 1 to 8 carbon atoms, up to 20% by weight of a monomer copolymerizable with these, or a monomer mixture consisting of both. () 45-99
, 9% by weight of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms and 0.1 to 10% by weight of a polyfunctional grafting agent, or together with 5% by weight or less of a polyfunctional A monomer mixture consisting of a crosslinking agent, a monomer copolymerizable with these at 40% by weight or less, or both, and having a Tg of 25° C. or lower when polymerized in the absence of the first layer. , a second layer polymerized in the presence of the first layer, (l) methyl methacrylate alone or together with 20% by weight or less of an alkyl group having 1 to 8 carbon atoms;
at least one alkyl acrylate or 2
The third layer has a Tg of 25° C. or higher, which is obtained by polymerizing 0% by weight or less of a monomer copolymerizable with these, or a monomer mixture consisting of both in the presence of the second layer. 3
The resulting three-layer structure polymer has a first layer of 5 to 30% by weight, a second layer of 40 to 85% by weight, and a third layer of 10 to 30% by weight. It is characterized by having a diameter of 200 to 900λ.

The first object of the present invention is to provide an acrylic resin with improved solvent resistance without impairing the characteristics of acrylic resins, such as transparency, weather resistance, and processability.

The second objective is to provide an acrylic resin modifier with good productivity. The hard thermoplastic acrylic resin used in the present invention is methyl methacrylate alone or together with it.
20% by weight or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms or 20% by weight
It can be obtained by polymerizing a monomer copolymerizable with the following monomers, or a monomer mixture consisting of both as necessary, by a known method.

The three-layer structure polymer used in the present invention is prepared according to a known method.
Obtained by emulsion polymerization.

In this case, it is necessary that no new particles be generated during polymerization of the second and third layers, and a sheet polymerization method is employed for this purpose. That is, when polymerizing the second and third layers, it is necessary not to add a new emulsifier, or if it is necessary to add it, it is necessary to keep it within a range where new particles are not generated. The first layer of the three-layer structure polymer is 5
5-99.9% by weight of methyl methacrylate and 0.1
~5% by weight of a polyfunctional grafting agent, or
20% by weight or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms or 20% by weight
Consisting of a hard acrylic resin with a Tg of 25°C or higher, preferably 50°C or higher, obtained by polymerizing a monomer copolymerizable with the following monomers, or a monomer mixture consisting of both as necessary, Contains a polyfunctional grafting agent as a component.

The polyfunctional grafting agent is a monomer having a plurality of copolymerizable functional groups with different reactivities in one molecule, and has the function of chemically bonding the first layer and the second layer. If this is not contained, whitening is likely to occur when stress is applied to the resulting resin. The polymer of the second layer is 45 to 99.9
At least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms in weight% and 0.1 to 10% by weight
a polyfunctional grafting agent, or a monomer mixture consisting of these, 5% by weight or less of a polyfunctional crosslinking agent, 40% by weight or less of a monomer copolymerizable with these, or both as necessary. is an acrylic elastic body whose Tg is 25°C or less, preferably 0°C or less when polymerized in the absence of the first layer, and the lower the Tg, the better the resulting resin's solvent resistance at low temperatures. Excellent quality.

Alkyl acrylate polymers have a lower refractive index than methyl methacrylate-based polymers, so when transparency is required, alkyl acrylates can be co-coated with monomers that give the polymer a higher refractive index. Polymerization increases the refractive index of the elastic body and improves its transparency. Also, a polyfunctional grafting agent is used to create a chemical bond between the second layer and the third layer. Without this, the resulting resin may glaze or whiten when stressed, exposed to solvents, or exposed to ultraviolet light. By using a polyfunctional grafting agent, the elastic body of the second layer can have a crosslinked structure to some extent, but if necessary, it is possible to further crosslink by using a polyfunctional crosslinking agent. The third layer polymer can be copolymerized with methyl methacrylate alone, or with at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms in an amount of up to 20% by weight, or with up to 20% by weight of these. This is a polymer obtained by polymerizing a monomer or, if necessary, a monomer mixture consisting of both in the presence of a second layer.

When this polymer is polymerized in the absence of a second layer,
Tg is 25°C or higher. The polymer of the third layer is graft-bonded with the second layer to improve the compatibility between the elastic body and the blend resin, thereby improving stress whitening resistance, and by coating the elastic body, it improves the particle size. It has the effect of eliminating stickiness and improving handleability. The weight ratio of each layer in the three-layer polymer is 5 to 30% by weight for the first layer, 40 to 85% by weight for the second layer, and 10 to 30% by weight for the third layer.

When the amount of the first layer is less than 5% by weight, sheet polymerization is often not completed, and when it is more than 30% by weight, a sufficient effect of improving solvent resistance cannot be obtained. The third layer is 1
If it is less than 0% by weight, the obtained three-layer structure particles will become sticky and have poor handling properties, and at the same time, the compatibility with the blend resin will decrease, resulting in poor dispersion of the particles into the blend resin. When producing a three-layer structure polymer by emulsion polymerization, the particle size can be controlled by the amount of emulsifier, and in order to obtain the desired effect in the present invention, it is necessary to strictly control the particle size. The particle size of the three-layer structure polymer used in the present invention needs to be in the range of 200 to 900λ. 200
When it is smaller than λ, the fluidity of the obtained resin is significantly reduced, and when it is larger than 900λ, the solvent resistance and stress whitening resistance are also reduced.

In particular, it has not been known at all that solvent resistance is affected by particle size, and the reason for this is not clear. The particle size can be measured in the state of the emulsion at the end of emulsion polymerization by known methods such as microscopy, absorbance method, and light scattering method.

In addition, when blended with acrylic resin, it can be measured using an electron microscope, but in this case, the third layer dissolves uniformly with the blend resin, so the outline of the second layer can be observed using an electron microscope, and the particle size appears small. . What should be particularly emphasized is that the three-layer structured polymer of the present invention has extremely superior productivity compared to conventionally proposed polymers.

In the case of emulsion polymerization, it is widely known that as the amount of emulsifier increases, the resulting polymer particles become smaller and the polymerization rate increases. The three-layer structure polymer of the present invention has a particle size of 200 to 9
00λ, which is smaller than other proposals, resulting in a high polymerization rate, and since the structure is simple with three layers, productivity is particularly excellent. The carbon number of the alkyl group used in the hard thermoplastic acrylic resin and three-layer structure polymer of the present invention is 1 to 8.
Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate.

These can be used alone or as a mixture of two or more. Particularly preferred among these are n-butyl acrylate and 2-ethylhexyl acrylate. In addition, copolymerizable monomers used in the rigid thermoplastic acrylic resin and three-layer structure polymer of the present invention include aromatic unsaturated monomers represented by styrene, and unsaturated nitriles represented by acrylonitrile. Examples include vinyl monomers such as monomers, higher acrylates, and higher methacrylates.

In particular, as a monomer for adjusting the refractive index, styrene, phenyl methacrylate, naphthyl methacrylate, etc. are preferable. Examples of the polyfunctional grafting agent used in the first and second layers of the three-layer structure polymer of the present invention include allyl esters such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid, particularly allyl methacrylate and Allyl acrylate is preferred.

In addition, examples of the polyfunctional crosslinking agent used in the second layer of the three-layer structure polymer include acrylic polyalkylene glycol, diester of methacrylic, and divinylbenzene. Polyethylene glycol dimethacrylate and polyethylene glycol diacrylate are preferred. As the polymerization initiator used in the polymerization of the three-layer structure polymer of the present invention, those commonly used in radical polymerization can be used, but
In particular, redox-based polymerization initiators are preferred.

In addition, additives commonly used in polymerization, such as chain transfer agents and ultraviolet absorbers, can also be optionally used. Anionic surfactants are used as the emulsifier used in polymerization to obtain the three-layer structure polymer, but the emulsifier is not necessarily limited thereto.

The hard thermoplastic acrylic resin to be blended is produced by a batch or continuous method such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization according to commonly used known methods. The solvent-resistant acrylic resin composition of the present invention contains 20 to 98 parts by weight of the hard thermoplastic acrylic resin obtained by the method of the present invention and 2 to 80 parts by weight of the three-layer structure polymer, when the total amount is 100 parts by weight. obtained by blending parts.

If the amount of the three-layer polymer is less than 2 parts by weight based on 100 parts by weight of the total amount, the solvent resistance and stress whitening resistance will be extremely reduced.

The thus obtained resin composition of the present invention is a solvent-resistant acrylic resin composition that has improved solvent resistance without impairing transparency, weather resistance, and processability, and has good productivity. .

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

The particle size in the Examples was measured using an electron microscope.

Solvent resistance was determined by supporting an injection-molded tamper at one end with a fulcrum, applying a load to the other end, and dropping solvent onto the fulcrum to examine the relationship between the time it takes for the test piece to break and the surface stress of the test piece. ,
The average of the 5 test scores was taken.

Impact resistance was measured by V-notched Izot strength according to ASTM-D256. For whitening, pull the specimen
The whitening state at a predetermined elongation rate was visually inspected.

Fluidity (melt flow index, hereinafter abbreviated as MI)
was measured by the method of ASTM-Dl238 at 230°C and a load of 3.81<9.

Example 1 In a 101 beaker equipped with a stirrer and a condenser,
Add 5.71 g of distilled water, 219 g of sodium dioctyl sulfosuccinate as an emulsifier, and 1.2 g of Rongalit as a reducing agent, and dissolve uniformly.

First layer.・As methyl methacrylate 2209, n
-Butyl acrylate 7', allyl methacrylate 0.
A homogeneous solution of 69, n-octyl mercaptan, 0.79, and diisopropylbenzene hydroperoxide, 0.239, was added and polymerized at 80°C. After about 15 minutes, the reaction temperature rose rapidly, indicating that the polymerization was complete. Next, as the second layer, n-butyl acrylate 13009 and styrene 300f! , diethylene glycol diacrylate 12
9, allyl methacrylate 179, and diisopropylbenzene hydroperoxide 1.69 were added dropwise over 1 hour. Approximately 40 minutes after the completion of the dropwise addition, the reaction temperature reached a peak, indicating that the reaction was complete. Then, as the third layer, methyl methacrylate 6409, n-
When a homogeneous solution of 409% of butyl acrylate, 2.09% of n-octyl mercaptan, and 0.79% of diisopropylbenzene hydroperoxide was added, the reaction temperature reached a peak after about 30 minutes. Then, the reaction temperature was raised to 95°C and the reaction was continued for 1 hour. The particle size of this polymer was approximately 890 particles. The obtained emulsion was poured into a 0.501) aluminum chloride aqueous solution to coagulate the polymer. Add this with warm water for 5 minutes.
After washing twice, it was dried to obtain a three-layer structure polymer. On the other hand, acrylic resin beads with an average molecular weight of 100,000 containing 97% by weight of methyl methacrylate and 3% by weight of n-butyl acrylate were made by a conventional suspension polymerization method and blended with the above three-layer structure polymer at a predetermined ratio. It was made into pellets.

Using this, various test pieces were molded and subjected to measurements. The results are shown in Table 1.

Examples 2 to 5 Various test pieces were molded and subjected to measurements in the same manner as in Example 1 except that the particle size was changed.

The results are shown in Table 2. Comparative Examples 1 to 5 Various test pieces were molded and subjected to measurement in the same manner as in Example 1 except that the particle size was changed.

Claims (1)

[Scope of Claims] 1 When the total is 100 parts by weight, (A) methyl methacrylate alone, or 20% by weight or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms; Rigid thermoplastic acrylic resin 20-98 made by polymerizing 20% by weight or less of a monomer copolymerizable with these, or a monomer mixture consisting of both.
A solvent-resistant acrylic resin composition comprising a blend of parts by weight and 2 to 80 parts by weight of (B) a three-layer structure polymer,
The three-layer structure polymer contains (I) 55 to 99.9% by weight
methyl methacrylate and 0.1 to 5% by weight of a polyfunctional grafting agent, or together with at least 20% by weight of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms; or 20% by weight or less of alkyl acrylate; A first layer consisting of a hard polymer having a Tg of 25° C. or higher, obtained by polymerizing a monomer copolymerizable with these, or a monomer mixture consisting of both, (II) 45-99 .9% by weight of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms and 0.1 to 10% by weight of a polyfunctional grafting agent, or together with not more than 5% by weight of polyfunctionality. A monomer mixture consisting of a crosslinking agent, a monomer copolymerizable with these at 40% by weight or less, or both, and having a Tg of 25° C. or lower when polymerized in the absence of the first layer. , the second layer polymerized in the presence of the first layer, (I
II) Methyl methacrylate alone, or 20% by weight or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms, or 20% by weight or less of a monomer copolymerizable with these, or both. T, which is obtained by polymerizing a monomer mixture consisting of T in the presence of a second layer.
It has a three-layer structure consisting of a third layer in which g is 25°C or higher,
And the obtained three-layer structure polymer has a first layer of 5 to 30% by weight.
, the second layer consists of 40 to 85% by weight, the third layer consists of 10 to 30% by weight (total 100% by weight), and the particle size is 200 to 9.
An acrylic resin composition characterized in that it has a thickness of 00 Å. 2. The acrylic resin composition according to claim 1, wherein the alkyl acrylate whose alkyl group has 1 to 8 carbon atoms used in the hard thermosetting acrylic resin and the three-layer polymer is n-butyl acrylate. 3. The acrylic resin composition according to claim 1, wherein the polyfunctional grafting agent used in the first layer and second layer of the three-layer structure polymer is allyl methacrylate. 4. The acrylic resin composition according to claim 1, wherein the polyfunctional crosslinking agent used in the second layer of the three-layer structure polymer is diethylene glycol diacrylate. 5. The acrylic resin composition according to claim 1, wherein the copolymerizable monomer used in the second layer of the three-layer structure polymer is styrene.