KR20050079296A - Acrylic impact modifiers with improved thermal stability and manufacturing method thereof - Google Patents

Abstract

The present invention is an inner layer consisting of a glassy methyl methacrylate or a methyl methacrylate copolymer, an intermediate layer grafted on the inner layer and a rubbery butyl acrylate copolymer or butadiene copolymer, and a graft on the intermediate layer In a three-layer acrylate impact modifier having an outer layer composed of a glass-like methyl methacrylate or a methyl methacrylate copolymer, the transparent acrylic system composed of the copolymer obtained by including the intermediate layer with an aromatic acrylate monomer. As the impact modifier is provided, when the aromatic acrylate monomer is used in the intermediate layer composition, thermal stability is improved as compared with the conventional aromatic vinyl monomer, so that discoloration does not occur due to vacuum drying for a long time. Possible cabinet Has a point.

Description

Transparent impact modifiers with improved thermal stability and manufacturing method

The present invention relates to a transparent acrylic impact modifier with improved thermal stability and a method for manufacturing the same, and more particularly, to a transparent acrylic impact modifier capable of processing without deterioration of transparency due to improved thermal stability and a method of manufacturing the same.

Conventionally, impact modifiers for transparent acrylic resins include methyl methacrylate-butadiene-styrene (hereinafter referred to as MBS), acrylonitrile-butadiene-styrene (hereinafter referred to as ABS), and acrylate impact modifiers. . Among them, in case of MBS-based or ABS-based impact modifiers, butadiene gas is used during manufacturing, and the manufacturing process is very cumbersome. Due to low weather resistance, physical properties are degraded when used outdoors for a long time, and refractive index is different, which greatly reduces transparency. In addition, ABS-based impact modifiers have the disadvantage of using more impact modifiers in order to exhibit the same impact reinforcement effect.

As a representative impact modifier that improves weather resistance and impact strength while compensating for such problems, an acrylate-based impact modifier may be mentioned. An acrylate impact modifier is prepared by cross-polymerizing vinyl monomers such as (meth) acrylic monomers, styrene derivatives and vinyl derivatives, surfactants, initiators, crosslinking agents and graft agents. The acrylic impact modifier transfers the externally applied impact from the matrix resin to the acrylic rubber layer, and the energy is absorbed and diverged from the rubber layer, thereby providing an excellent impact strengthening effect.

Looking at one example of the specific acrylate-based impact modifier, an acrylate-based impact modifier having a three-layer structure is prepared through the following three-step emulsion polymerization process:

i) emulsion polymerization (conversion rate: 90-95%) of the first monomer in the presence of ion-exchanged water, emulsifier, crosslinking agent and polymerization initiator to prepare an emulsion of glassy polymer (inner layer) particles having an average particle diameter of 50-250 nm; ii) The second monomer, the emulsifier and the crosslinking agent are added dropwise thereto, followed by emulsion polymerization, and at the completion of the polymerization, a polymerization initiator is added to graf the rubbery polymer (intermediate layer) onto the glassy polymer (inner layer) to obtain an average particle diameter. An emulsion of the particles having a thickness of 200 to 300 nm was prepared (conversion rate: 91 to 95%); iii) The third monomer is added dropwise thereto, followed by emulsion polymerization, and in the polymerization completion step, a polymerization initiator is added, and a glass polymer (outer layer) is grafted onto the rubber polymer (intermediate layer), thereby obtaining an average particle diameter of 250 to 350 nm. To prepare a impact modifier.

In this case, as the monomer of the rubbery polymer, an aromatic vinyl monomer is included, and examples thereof include styrene. In this way, the aromatic vinyl monomer is included to match the refractive index of the acrylic resin. By the way, the aromatic vinyl monomer has a disadvantage that it can be easily oxidized by heat, there is a problem that the impact modifier discolors in the process of drying the final impact modifier. This property can also be a factor in lowering productivity during drying. In addition, there is a difference in the reactivity with the acrylic monomer, there is a possibility that it may exist as a homopolymer, and when applied to the acrylic resin may be a factor that reduces the transparency.

Such a method of manufacturing an impact modifier is disclosed in Korean Patent Laid-Open Nos. 2001-0062869, 2001-0071504, 2002-0022351, JP-A-1980-148729, 1971-31462, 1979-1584, and the like. .

Therefore, the inventors of the present invention while trying to solve the problem of discoloration due to the rubber-like polymer of the acrylate-based impact modifier having a three-layer structure, as a result of using the aromatic acrylate monomer in place of the aromatic vinyl monomer, The present invention has been completed by improving the stability to prevent discoloration and improving transparency.

SUMMARY OF THE INVENTION An object of the present invention is to provide an acrylic impact modifier that prevents discoloration by increasing the thermal stability by forming a rubbery polymer, that is, an intermediate layer, including an aromatic acrylate monomer.

Another object of the present invention is to provide a method for producing an acrylic impact modifier comprising an intermediate layer obtained from the aromatic acrylate monomers as described above.

Transparent acrylic impact modifier of the present invention for achieving the above object is a cabinet layer consisting of a glass-like methyl methacrylate or methyl methacrylate copolymer; An intermediate layer grafted to the inner layer and composed of a rubbery butyl acrylate copolymer or butadiene copolymer; And an outer layer composed of a glassy methyl methacrylate or a methyl methacrylate copolymer grafted to the intermediate layer, wherein the intermediate layer is obtained by containing an aromatic acrylate monomer. It is characterized by consisting of a copolymer.

The method of manufacturing an acrylic impact modifier as described above comprises i) emulsion-polymerizing a first monomer comprising a methyl methacrylate or a methacrylate monomer in the presence of ion-exchanged water, an emulsifier, a crosslinking agent and a polymerization initiator. Inner layer) preparing an emulsion of particles; ii) a second monomer, an emulsifier, and a crosslinking agent containing butyl acrylate or butadiene and an aromatic acrylate monomer are added dropwise thereto, followed by emulsion polymerization, and a polymerization initiator is added to the glass-like polymer (inner layer) phase in the polymerization completion step. Preparing an emulsion of particles to which the rubbery polymer (intermediate layer) is grafted; iii) A third monomer containing a methyl methacrylate or methacrylate monomer is added dropwise thereto, followed by emulsion polymerization, and a polymerization initiator is added at the completion of the polymerization to give a glassy polymer (other than Each layer).

The present invention will be described in more detail as follows.

The present invention uses an aromatic acrylate compound instead of an aromatic vinyl compound as a rubbery polymer of an acrylate impact modifier having a conventional three-layer structure, that is, an intermediate layer monomer.

When the aromatic acrylate monomer is used instead of the aromatic vinyl monomer, its structural characteristics make it difficult to generate radicals due to heat compared to the aromatic vinyl monomer, thereby increasing thermal stability during drying and ultimately preventing discoloration. This can increase productivity during drying and improve the transparency of the impact modifier.

Examples of the aromatic acrylate compound that plays such a role include, but are not limited to, benzyl methacrylate, benzyl acrylate, benzyl acrylate.

Other used monomers are roughly the same as in conventional acrylate based impact modifiers.

Specifically, the manufacturing method is as follows.

i) emulsion polymerization of the first monomer in the presence of ion-exchanged water, an emulsifier, a crosslinking agent and a polymerization initiator to prepare an emulsion of the glassy polymer to prepare an inner layer.

More specifically, a solution in which ion exchanged water, an emulsifier, a crosslinking agent, and a part of a first monomer are mixed is introduced into a reactor, and the solution is heated and stirred. When the temperature of the solution reaches 60 to 90 ° C, a polymerization initiator is introduced. Emulsion polymerization is carried out, and when the emulsion is formed, the polymerization is continued while dropwise addition of the remaining amount of the first monomer, and when the emulsion polymerization is completed, the polymerization initiator is added again to prepare an emulsion of the glass polymer (particle).

In this process, the average particle diameter of the glassy polymer (inner layer) is proportional to the first monomer content and the amount of emulsifier used. Lowering the content of the first monomer to reduce the size of the glassy polymer is advantageous because it can form more rubbery polymer in the impact modifier. It is usually appropriate that the amount of the first monomer used is 5 to 30 parts by weight based on the total monomers. The average particle diameter of a glassy polymer is 50-250 nm normally. In this step, it is preferable to emulsify and polymerize so that the ratio (conversion) of the first monomer to the glass polymer is 90 to 95%.

As the first monomer, at least one monomer selected from the group consisting of alkyl methacrylate having 1 to 20 carbon atoms, alkyl aryl ester having 1 to 20 carbon atoms and fluoroalkyl ester having 1 to 20 carbon atoms may be used. Can be mentioned.

In addition, the ion-exchanged water is produced through an ion exchange group, and the metal ion concentration is preferably 2 ppm or less, and may be used at 100 to 500 parts by weight based on the first monomer.

Ii) preparing an emulsion of rubbery polymer particles grafted onto the glassy polymer by adding a second monomer, an emulsifier and a crosslinking agent dropwise onto the inner cabinet layer, and then adding a polymerization initiator in an emulsion polymerization completion step.

While the emulsion of the glassy polymer is stirred at 60 to 90 ° C, the polymerization is continued while dropwise adding an emulsifier, a crosslinking agent and a second monomer, and the polymerization initiator is added again when the polymerization is completed. By this emulsion polymerization, a rubbery polymer (intermediate layer) is grafted on a glassy polymer (inner layer). The higher the content of the rubbery polymer (intermediate layer) in the impact modifier, the more the impact resistance is usually improved.

Here, the second monomer essentially includes an aromatic acrylate monomer, and in addition, alkyl methacrylate having 1 to 20 carbon atoms, alkyl aryl ester having 1 to 20 carbon atoms and methacrylic acid having 1 to 20 carbon atoms. Two or more types of monomers selected from fluoroalkyl esters can be used.

The amount of the second monomer having such a composition is usually 50 to 80 parts by weight relative to the total monomers, and the amount of the aromatic acrylate monomer is preferably 5 to 50% by weight in the intermediate monomer composition. If the amount of the aromatic acrylate monomer is out of the above range, there may be a haze problem when the acrylic resin is applied.

It is preferable that the average particle diameter of the particle | grains (an inner layer + middle layer) in which the rubbery polymer was grafted on the glassy polymer is 200-300 nm.

In the above step, it is preferable to perform emulsion polymerization so that the ratio (conversion) of the second monomer to the rubbery polymer is 91 to 95%.

Iii) preparing an impact modifier in which the glass polymer is grafted onto the rubber polymer by adding the polymerization monomer to the rubber polymer emulsion, followed by emulsion polymerization, and adding a polymerization initiator in the emulsion polymerization completion step.

As a final step, the polymerization initiator and the third monomer are continuously added dropwise to the emulsion in which the two-step emulsion polymerization is completed, and the polymerization initiator is added again at the point where the emulsion polymerization is completed, and the glass phase on the rubber-like polymer (intermediate layer) An emulsion of particles to which the polymer (outer layer) is grafted is prepared.

In this process, controlling the thickness of the glass polymer (outer layer) grafted onto the rubber polymer to be 10% or less of the total thickness of the impact modifier shortens the mixing time with the matrix resin and increases the rubber polymer content. It is advantageous to.

To this end, the amount of the third monomer is preferably 10 to 40% by weight based on the total monomers. As the third monomer, at least one monomer selected from the group consisting of alkyl methacrylate having 1 to 20 carbon atoms, alkyl aryl ester having 1 to 20 carbon atoms and fluoroalkyl ester having 1 to 20 carbon atoms may be used. Can be used.

The average particle diameter of the impact modifier of the present invention prepared after the above step is preferably adjusted to 250 to 350nm.

In the above process, it is preferable to perform emulsion polymerization so that the ratio (conversion) of the third monomer to the glass-like polymer is 92% or more.

If the conversion rate is low, the thermal stability of the polymer is lowered, so that pyrolysis occurs during processing.

In the first half of the process, the emulsifiers (surfactants) are sodium or potassium salts of alkyl sulfates having 4 to 30 carbon atoms. Specifically, sodium dodecyl sulfate, sodium dioctyl sulfoxysinate, sodium dodecyl benzene sulfate, etc. can be used. In order to improve the thermal stability of the polymer, the emulsifier is preferably a water-soluble substance. It is appropriate to use the emulsifier 0.2 to 4 parts by weight based on the total monomers.

As crosslinking agent, 1, 2- ethanediol dimethacrylate, 1, 3- propanediol dimethacrylate, 1, 4- butanediol dimethacrylate, 1, 5- pentanediol dimethacrylate, 1, 6- Hexanediol dimethacrylate, divinylbenzene, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, butylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene Glycol dimethacrylate, polybutylene glycol dimethacrylate, allyl methacrylate, etc. can be used, The usage-amount is preferable 0.1-15 weight part with respect to all monomers.

As the polymerization initiator, cumene hydroperoxide, potassium persulfate or sodium persulfate, an azo water-soluble initiator, or the like can be used. The amount of these to be used is preferably 0.02 to 2.0 parts by weight based on the total monomers.

When the polymerization is completed, an emulsion of three-layered particles (average particle size 250 to 350 nm) is obtained.

The emulsion is slowly added dropwise to 1% magnesium sulfate or 1% calcium chloride solution preheated to 70-90 ° C. to stir to precipitate particles in the emulsion. Instead of using salt, it can also be precipitated with a spray dryer.

The precipitated particles were washed three to four times with distilled water at about 70 ° C., and then dried in a vacuum oven at 60 ° C. for several days to prepare an impact modifier as a final product.

The impact modifier obtained in this way comprises: i) an inner layer of the glass polymer of the first monomer, ii) an intermediate layer of the rubbery polymer of the second monomer grafted to the inner layer, and iii) a second layer grafted on the intermediate layer. It is a granular material of a three-layer structure which has an outer layer which is a trimeric glass-like polymer.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Comparative Example 1

i) 1,000 g of secondary distilled water was added to a 3 L container, and the internal temperature was heated to 80 ° C. under a nitrogen stream, followed by 170.3 g of methyl methacrylate, 9.0 g of ethyl acrylate, 0.7 g of allyl methacrylate, and sodium dioctyl sulfostone. 38 g of a mixed solution of 1.35 g of sinate was added to the reactor, followed by stirring for 15 minutes.

Then, 15 ml of 1% potassium persulfate solution was added thereto, followed by stirring for 60 minutes. When the polymerization was almost complete, the remaining mixed solution was added dropwise to the reactor at a rate of 5 g per minute. After completion of the dropwise addition, the reaction was further performed for 60 minutes to prepare an emulsion of a glassy polymer (inner layer) having an average particle diameter of 180 nm. [94% conversion rate]

Ii) 25 ml of 1% potassium persulfate solution was added thereto and stirred for 15 minutes, followed by 8 g / min of a mixed solution of 264 g of butyl acrylate, 60 g of styrene, 6.5 g of allyl methacrylate, and 2.5 g of sodium dioctylsulfosuccinate. Was added dropwise to the reactor at the rate of. After completion of the dropwise addition, 25 ml of 1% potassium persulfate solution was added. After completion of the dropwise addition, the mixture was further polymerized for 240 minutes, and then 12 ml of 1% potassium persulfate solution was added to the reactor for further 15 minutes to polymerize the rubber-like polymer (intermediate layer) on the inner layer. An emulsion was prepared. [Conversion 94%].

Iii) Here, a mixture solution of 86 g of methyl methacrylate and 4.5 g of ethyl acrylate is added dropwise to the reactor at a rate of 3 g per minute, and then polymerization is further performed for 100 minutes to complete the polymerization. An emulsion of grafted particles (average particle diameter 298 nm) was prepared.

The emulsion was added dropwise to a 1% magnesium sulfate solution preheated to 80 ° C. to prepare a powdered solid. The powder was filtered, washed with distilled water at 70 ° C. three times, and dried in a vacuum oven at 60 ° C. for 2 days to prepare an impact modifier.

Example 1

The impact modifier was prepared in the same manner as in Comparative Example 1, except that benzyl methacrylate was used instead of styrene in the step ii) emulsion polymerization process.

Experimental Example

454 g of impact modifiers obtained according to Comparative Examples 1 and 1 and 8 g of Tinuvin-312 as an additive, 4 g of Irganox B-900 and 0.04 g of Uvitex OB And after mixing with 1,545g acrylic resin and extrusion molding to produce a shock-resistant acrylic specimen of 4.8mm.

The color of the obtained acrylic specimen was evaluated and the results are shown in Table 1 below.

Color, total light transmittance (TT) and haze were measured by CIE and ASTM methods.

Color TT / Haze L a b YI TT Haze Example 1 96 0.13 0.62 1.49 90.99 1.41 Comparative Example 1 95.58 0.05 1.73 3.57 90.64 1.53

Each sample obtained was evaluated for color after drying in a vacuum oven at 60 ° C. for 2 days or 6 days in a vacuum oven at 80 ° C., and the results are shown in Table 2 below.

Color Drying condition L a b YI Example 1 98.29 -1.03 0.36 0.1 2 days in a vacuum oven at 60 ℃ Comparative Example 1 97.7 -1.1 0.8 0.57 Example 1 97.78 -0.96 0.45 0.18 2 days in a vacuum oven at 80 ℃ Comparative Example 1 97.32 -1.18 1.1 1.53

From the results of Table 2, YI value of using a aromatic acrylate monomer such as benzyl methacrylate instead of styrene as a monomer of the rubber polymer (intermediate layer) is less discoloration even when dried in a vacuum oven for a long time This can be confirmed from.

As described in detail above, the impact modifier of the present invention uses an aromatic acrylate monomer in the intermediate layer composition, thereby improving thermal stability as compared with using an aromatic vinyl monomer, and thus discoloring even after long-term vacuum drying. It has the advantage that it can be processed without.

Claims (5)

A cabinet layer composed of a glassy methyl methacrylate or a methyl methacrylate copolymer; An intermediate layer grafted to the inner layer and composed of a rubbery butyl acrylate copolymer or butadiene copolymer; And an outer layer composed of a glassy methyl methacrylate or a methyl methacrylate copolymer grafted to the intermediate layer, wherein the intermediate layer is obtained by containing an aromatic acrylate monomer. Transparent acrylic impact modifier composed of a copolymer. The method of claim 1, wherein the aromatic acrylate monomer is a transparent acrylic impact modifier, characterized in that contained in 5 to 50% by weight of the total monomer of the intermediate layer. The transparent acrylic impact modifier according to claim 1 or 2, wherein the aromatic acrylic monomer is at least one selected from benzyl methacrylate, benzyl acrylate and benzyl acrylate. i) preparing an emulsion of glassy polymer (inner layer) particles by emulsion polymerization of a first monomer comprising a methyl methacrylate or methacrylate monomer in the presence of ion-exchanged water, an emulsifier, a crosslinking agent and a polymerization initiator; ii) a second monomer, an emulsifier, and a crosslinking agent containing butyl acrylate or butadiene and an aromatic acrylate monomer are added dropwise thereto, followed by emulsion polymerization, and a polymerization initiator is added to the glass-like polymer (inner layer) phase in the polymerization completion step. Preparing an emulsion of particles to which the rubbery polymer (intermediate layer) is grafted; And iii) A third monomer containing a methyl methacrylate or methacrylate monomer is added dropwise thereto, followed by emulsion polymerization, and a polymerization initiator is added at the completion of the polymerization to give a glassy polymer (other than Each layer) method for producing a transparent acrylic impact modifier comprising the step of forming. [5] The method of claim 4, wherein the aromatic acrylate monomer is used in the step of emulsion emulsion polymerization so as to be 5 to 50% by weight in the intermediate layer monomer.