JP3059743B2 - Impact resistant acrylic resin laminated sheet with excellent optical properties and weather resistance - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an impact-resistant acrylic resin sheet having excellent optical properties and excellent weather resistance.

[Conventional technology]

Acrylic resin is a thermoplastic resin that is excellent in transparency, beauty, weather resistance, printing characteristics, etc. By utilizing these characteristics, signboards, displays, lighting covers, exteriors, doors, etc.
It is used in many fields such as music and stationery.

Among these applications, for example, signs, vending machine face plates, lighting covers, sun visors for automobiles, etc., are required to be resistant to various impacts, that is, impact resistance.

In response to this demand, an impact-resistant acrylic resin to which an acrylic or butadiene-based elastic polymer is added as a modifier has been developed.

However, in the sheet molded article using this impact-resistant acrylic resin, optical properties such as transparency and glossiness and weather resistance, which are great advantages of the general acrylic resin, are reduced due to the effect of the added modifier. There is a problem.

However, this problem is that it is lower than that of general acrylic resin. In the impact-resistant acrylic resin sheet, the impact resistance of general acrylic resin is remarkably improved. It is widely used in applications that require improvement in quality. If the problems addressed in the present invention are improved, the application of the impact-resistant acrylic resin sheet is further expanded, and this has been expected in the art.

It is generally thought that the decrease in optical properties is due to the addition of a foreign modifier in the general acrylic resin, and the decrease in weather resistance is due to the deterioration in transparency and discoloration due to the modifier being altered by exposure to the outdoors. Have been.

Conventionally, when improving weather resistance, it is common to improve the weather resistance by adding an additive such as an ultraviolet absorber or an antioxidant. In order to obtain a sufficient effect with only a small amount, it is necessary to add a large amount of the additive.

However, if a large amount of additives is blended, the essential resin properties are variously reduced, and coloring is likely to occur, which leads to an increase in cost.

On the other hand, a method for improving the optical characteristics of an impact-resistant acrylic resin sheet has not yet been proposed so far.

[Problems to be solved by the invention]

The object of the present invention is to solve the above-mentioned problems of the conventional impact-resistant acrylic resin, and has excellent optical properties and weather resistance,
Another object of the present invention is to provide an acrylic resin laminated sheet which satisfies impact resistance and does not cause problems such as delamination even when thermoformed.

[Means for solving the problem]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, provided a general-grade acrylic resin layer having a specific thickness on one or both sides of an impact-resistant acrylic resin layer, and the optical characteristics of the acrylic resin layer within a certain range. The present inventors have found that the object can be achieved by the above-described method, and have reached the present invention.

That is, the present invention provides an elastic body that exhibits a rubbery state at room temperature in a continuous resin phase containing methyl methacrylate as a main component and has a particle size of 0.
General acrylic resin having an impact-resistant acrylic resin dispersed discontinuously in a particle size of 15 to 4 μm in an amount of 5 to 70% by weight and having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms as a base material With a thickness of 0.5 μm to 100 μm on one or both sides of the base material part and a thickness such that the total thickness of the laminated part is within 30% of the thickness of the entire sheet. The present invention is to provide an impact-resistant acrylic resin laminated sheet having excellent weather resistance, having optical properties of 1.0% or less and gloss of 130% or more.

The generally used impact-resistant acrylic resin sheet has a higher impact strength than a general acrylic resin sheet, for example.
The Izod impact strength (with notch) is increased substantially, about 2 to 10 times, while other physical properties, such as optical properties such as transparency and gloss, strength and rigidity, weather resistance, heat resistance Usually, basic characteristics such as hardness and the like are deteriorated. However, as described above, the excellent impact resistance is a great advantage, and has been widely used in the field of application of acrylic resin as a hardly cracked sheet and a hardly cracked molded product.

The present inventors have worked on improving these problems of the impact-resistant resin sheet, and have observed the surface of the sheet with an electron microscope. As a result, the smoothness of the surface was smaller than that of a general acrylic resin sheet. What is worse, the surface layer of the sample whose haze (cloudiness) has increased due to outdoor exposure has a continuous uneven surface, and the surface is clearly larger than that before exposure. It has been found that the reason why the noise rises is that light is irregularly reflected on the uneven surface. This is due to the fact that rubber particles existing on the surface of the impact-resistant acrylic resin deteriorate due to outdoor exposure, the rubber part collapses, and eventually fall off from the surface together with the surrounding acrylic resin matrix part to form irregularities. It is considered to have been reached.

Based on this finding, the present inventors have focused on laminated sheets as one of the methods for improving the properties of impact-resistant acrylic resins that are lower than those of general acrylic resins. By laminating resin layers and keeping optical characteristics within a certain range, a laminated sheet having improved optical characteristics and weather resistance almost equal to general acrylic resin sheets can be obtained while maintaining impact resistance. Was found to be. The improvement of optical properties such as transparency and glossiness in the present invention has a great significance to the industry in the past, while there has been no other way but effective methods.

That is, the optical properties of the impact-resistant acrylic resin sheet of the present invention are almost as good as those of a general acrylic resin sheet, and are evaluated by a haze value when evaluated by a measurement method described later. It is 1.0% or less, preferably 0.5% or less, and has a glossiness of 130% or more, preferably 135% or more.

Further, the sheet of the present invention is excellent also in terms of weather resistance, and its weather resistance is comparable to that of a general acrylic resin sheet, and the haze value after accelerated exposure is evaluated by the measurement method described later. It is 2% or less, preferably 1.5% or less, at which no haze is visually observed.

The impact-resistant acrylic resin used in the present invention is, for example, a dispersion of 5-70% by weight of an elastic body which exhibits a rubber-like state at normal temperature in a continuous resin phase containing methyl methacrylate as a main component and which is discontinuously dispersed. is there.

Here, the elastic material that exhibits a rubber-like shape at room temperature refers to, for example, a rubber-like elastic material such as an acrylate polymer, a rubber-like polymer containing butadiene as a main component, and an ethylene-vinyl acetate copolymer. Specific examples of the acrylate-based polymer include those having butyl acrylate, 2-ethylhexyl acrylate, or the like as a main component, and typical examples thereof include alkyl acrylate such as butyl acrylate and styrene. Particle elasticity in which a grafted rubber elastic component and a hard resin layer made of methyl methacrylate and / or a copolymer of methyl methacrylate and alkyl acrylate form a multilayer with a core-shell structure. There is a body.

Of these, particularly preferred are acrylate-based polymers containing butyl acrylate as a main component and rubbery polymers containing butadiene as a main component.

A rubber elastic body in the impact-resistant acrylic resin sheet,
In general, acrylate copolymers containing butyl acrylate as a main component generally have a particle size of about 0.09 μm to 4 μm, but include rubber elastomers having a large particle diameter. The impact-resistant acrylic resin sheet has a higher haze (cloudiness) than that of a rubber elastic body having a small particle diameter, and the transparency of the appearance is reduced. Therefore, in the present invention, the effect of improving the optical properties is remarkable in an impact-resistant acrylic resin sheet containing a rubber elastic body having a particle diameter of 0.15 μm or more and a rubbery polymer containing butadiene as a main component.

General acrylic resin used in the present invention, among acrylic resins commercially available as so-called general grade,
Alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms (hereinafter abbreviated as C) - it is an acrylic resin having a Units, extrusion, an alkyl group of C ₁ -C ₄ from the viewpoint of stability during other thermal processing It is preferable that the alkyl acrylate is copolymerized within 20% by weight.

The alkyl methacrylate having an alkyl group of the above-mentioned C ₁ -C ₄ - Examples of metropolitan methyl methacrylate - DOO, ethyl methacrylate - DOO, propyl methacrylate - DOO, butyl methacrylate - there are bets like, Of these, methyl and ethyl methacrylate are most preferred in terms of physical properties.

Further, an alkyl acryl having a C ₁ -C ₄ alkyl group
Methyl acrylate, ethyl acrylate,
Examples thereof include propyl acrylate and butyl acrylate, and preferred are methyl acrylate and ethyl acrylate. Further, the amount of the alkyl acrylate contained in the alkyl methacrylate is preferably 20% by weight or less, more preferably 0.5 to 13% by weight.

In the present invention, the thickness of the general acrylic resin layer laminated on the impact-resistant acrylic resin layer is extremely important, and the thickness must be specified in order to maintain the impact strength and to improve the optical characteristics and weather resistance. Must. That is, when the thickness of the laminated portion is increased, the original impact resistance of the base portion is reduced. On the other hand, when the thickness of the laminated portion is small, the effect of improving the optical characteristics and weather resistance is small. The present inventors have repeatedly evaluated this point, and as a result, it has been found that if the thickness is 0.5 μm or more at which the elastic particles are sufficiently covered, an effect on improvement of optical characteristics and weather resistance can be obtained. Preferably, the thickness of the laminated portion is 5 μm to further enhance the effect.
The above thickness is good.

When observing the surface of the impact-resistant acrylic resin laminated with general acrylic resin with an electron microscope, the thickness of the extremely thin laminated portion of 0.5 μm can be clearly evaluated and measured.
The interface between the two layers was sufficiently discernible although slight dispersion of the rubber particles in the base material portion was observed in the laminated portion.

Further, when the thickness of the laminated portion is 100 μ or more, the strength is reduced due to the notch effect against impact, which is not good. Preferably 50
μm or less is preferred. The thickness of the general acrylic resin layer of the laminated portion may be the minimum required thickness, and the thickness of the entire laminated sheet is preferably within 30%. If the thickness is more than this, the impact strength of the impact-resistant acrylic resin layer is greatly reduced, and the original features are impaired. Although the thickness of the laminated sheet of the present invention is not particularly limited,
Practically, it is preferably 2 mm or more in terms of sheet rigidity and strength.

The method of obtaining the laminated sheet (including the film) of the present invention includes a coextrusion method, a laminating method, and a coextrusion method.
There is a method such as
The co-extrusion method is preferred because a surface of the laminated sheet can be smooth. The co-extrusion method is excellent in that the fluidity of both layers can be matched and uniform at the time of lamination, so that the adhesion of both layers is good and the molding distortion is similar. Coextrusion uses two or more normal extruders, and the impact-resistant acrylic resin layer is a large extruder with 60mmφ, 90mmφ, 115mmφ, etc. For general acrylic resin lamination, 30mmφ, 45mmφ
Use a smaller extruder.

The laminate of the present invention can be basically applied to a film and a profile extrusion as well as a sheet. Further, the effects of the present invention can be similarly recognized and applied to various molded products obtained from the laminated sheet of the present invention.

In the case of a sheet, the control of the thickness of the laminated portion (general acrylic resin layer) and the base portion (impact-resistant acrylic resin layer) of the laminate is performed at the extruder output of two or more extruders and the extruder outlet. The film can be prepared by the roll clearance of a certain polishing roll. In the case of a film, the film can be prepared by controlling the output of two or more extruders and the roll speed of the take-up roll at the outlet of the extruder. or,
When producing a laminate, it is important to match the fluidity of the so-called substrate portion and the resin of the laminate portion, but this can be specifically performed by adjusting the temperature of the extruder.

The thickness of the laminated portion and the entire layer of the laminate is measured with a caliper when the thickness is 1 mm or more, and the thickness is measured when the thickness is 1 mm or less.
The cross section of the sample can be measured using a differential interference microscope or a commercially available thickness gauge (for example, PIG Universa manufactured by Big Malincklot, West Germany).
l (thickness gauge for dry film)) and 0.1mm (100μ
m) In the following cases, it can also be measured by a transmission electron microscope, an ATR (total reflection) method using an infrared spectrum, and a microinfrared method.

The laminate can be made transparent, translucent or opaque by blending an organic or inorganic dye or pigment in the laminate and / or the substrate. In addition, an ultraviolet absorber, a light stabilizer, an antioxidant, and the like can be added.

Furthermore, it is also possible to add a commercially available antistatic agent to the general acrylic resin part of the laminated part to impart antistatic properties to the final product, and to add a plasticizer to increase adhesion and affinity with the substrate part. It can also be blended.

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples.

The evaluation and test methods used in each of the examples and comparative examples are as follows.

(1) Evaluation of impact resistance Adopting the falling ball impact test, the device was fixed so that the four sides of the sheet sample of 10 cm square were not moved at an angle, and the center part was transparent with a 10 cm height gap. Stand up a plastic pipe vertically, drop a 2 kg steel ball through the pipe to determine the height at which the sample can be broken, and calculate this as (kg · c
m). In the case of double-sided lamination, an impact was applied to the front (front) surface of the sheet. The front side of the sheet here refers to the top of the sheet coming out of the polishing roll, and the back side refers to the opposite side.

(2) Evaluation of optical properties Haze and gloss (60
゜) is a digital haze meter from Nippon Denshoku Industries Co., Ltd.
It measured using.

(3) Evaluation of weather resistance Using the Suga Test Instruments Co., Ltd. Dupanel Optical Control Weatherometer (hereinafter abbreviated as QUV), the sample lamination surface (in the case of double-sided lamination, the sheet table (front) Haze of the sample at that time with 1500 HR irradiation with the) surface as the irradiation surface
Was measured using a cloudiness meter (NDH-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.

(4) Evaluation of thermoformability Vacuum was formed in a pen dish shape with a squeezing depth of 100 mm using a normal vacuum forming machine, and its appearance was observed and judged.

Production Example of Elastic Polymer In a reactor with a reflux condenser having an internal volume of 10
60 ml and 17.75 g of sodium dihexyl sulfosuccinate
75 ° C under nitrogen atmosphere while stirring at 250 rpm
The temperature rose. 534.6 g of methyl methacrylate (MMA),
Chill acrylate (BA) 19.4 g, allyl methacrylate
(ALMA) 0.443g and Tinuvin P 0.16 which is an ultraviolet absorber
The mixture consisting of 6 g is divided into two to three parts by weight, and the former is
(B1), the latter being (B2). (B1) in the above reactor
Five minutes after the addition, 0.22 g of ammonium persulfate was added, and 4
Hold for 5 minutes. Then (B2) continuously for 12 minutes
The mixture was added and kept for 20 minutes after the addition was completed. Gain in this way
The obtained polymer latex was cooled to 40 ° C. Then BA 11
41 g, styrene (St) 259 g, polyethylene glycol
Acrylate (PEGDA) (molecular weight 200) 3.64 g, ALMA 14.8
A mixture consisting of 4 g and Tinuvin P 0.42 g was added to the reactor.
And stirring was continued for 60 minutes. Heat this latex to 75 ° C
1.42 g of ammonium persulfate and hold for 190 minutes.
Was. Next, 876.1 g of MMA, 11.54 g of BA, and normal octylme
From 2.66 g of lucaptan (n-OM) and 0.27 g of tinuvin P
Divided into one to one, the former (B3), the latter
(B4). Next, put (B3) in the reactor continuously for 90 minutes
Was added. After the addition was completed, the mixture was kept for another 60 minutes. More anti
After adding 0.18 g of ammonium persulfate to the reactor,
(B4) is added continuously over 20 minutes, and 30 minutes after the addition is completed
Held. Next, the temperature was raised to 95 ° C. and maintained for 60 minutes. This
3% by weight sodium sulfate
Pour into warm aqueous solution, salt out, coagulate, then dehydrate,
After repeated washing, dry and remove the elastic polymer (R1).
Obtained. 20% by weight of this elastic polymer and Asahi Kasei Kogyo Co., Ltd.
Delpet LP-1 (Methyl methacrylate and methyl
80% by weight of acrylate copolymer)
After mixing for 20 minutes in a sir, twin screw extruder with 30mm vent
(Type A, manufactured by Nakatani Machine Co., Ltd.) at 240 ° C
Lettization was performed.

The particle size of the elastic polymer is changed by changing the emulsifier to, for example, sodium dioctylsulfosuccinate or by changing the monomer (B1) or (B2) addition rate in the same manner as in the above-mentioned production example of the elastic polymer. The obtained polymer was able to be synthesized. The elastic polymer thus obtained was dispersed in Delpet LP-1 as described above, stained with ruthenic acid, and the average particle size was measured using a transmission electron microscope. Table 1 shows the results.

Examples 1 to 6, Comparative Examples 1 to 4 Elastic polymer as impact-resistant acrylic resin for substrate
(R1, average particle size 0.25μm) 20% by weight and Delpet QP-
1 90mm diameter pellets made from 80% by weight, L / D
= 32 extruders, while the laminating section was used for Asahi Kasei Kogyo
Delpet LP-1 (methyl methacrylate and methyl alcohol)
Extruder with a diameter of 30mm and L / D = 32
Was used for co-extrusion of two types and two layers. Die is feed
It is a block type and the extruder temperature is 250 ~ 260 ℃
Was.

The thickness of the laminated sheet was adjusted by the opening degree of the die lip and the clearance of the polishing roll at the exit of the die, and the thickness of the laminated portion was adjusted by the throughput of both extruders. Thus, a laminated sheet having a sheet width of 80 cm was produced. This laminated sheet
And the thickness of the laminated portion were 3.0 mm and 10 μm, respectively (Example 1). The physical properties of the laminated sheet were evaluated by the methods described above. Table 2 shows the evaluation results obtained by changing the thickness of the laminated portion in various ways in the same manner.

In Table 2, the thickness of the laminated portion of the sheet obtained after stopping the extruder on the laminated portion was measured for the purpose of evaluating only the extremely thin samples of 0.5 μm and 0.3 μm in the laminated portion. The sample was used for evaluation. Further, as comparative examples, a sheet made of only a general acrylic resin in the laminated portion and a sheet made of only the impact-resistant acrylic resin in the base portion were separately manufactured and comparatively evaluated.

Examples 7 to 10, Comparative Examples 5 to 9 The base material was prepared by changing the particle size of the elastic polymer of the impact-resistant acrylic resin in the base material and changing the content of the elastic polymer to 30% by weight. In the same manner as in Example 1, a laminated sheet having a total thickness of 2.0 mm and a sheet made of only impact-resistant acrylic resin were prepared and evaluated for comparison. . Table 3 shows the results.

Examples 11 to 12 and Comparative Examples 10 to 12 Polymers and extruders using two or three layers of feed blocks for laminated sheets and other methods were the same as in Example 1, and A double-sided laminated sheet having a total thickness of 3.0 mm with various thicknesses was prepared, and for comparison, a sheet made of only impact-resistant acrylic resin was produced and evaluated. The results are shown in Table-4.

[Effects of the Invention] The impact-resistant acrylic resin laminated sheet of the present invention has significantly improved optical properties such as transparency and glossiness, as well as excellent weather resistance and impact resistance, as compared with conventional ones. And has the effect that delamination does not occur in thermoforming.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] An elastic body which exhibits a rubbery state at room temperature in a continuous resin phase containing methyl methacrylate as a main component has a particle size of 0.15 to 4 μm.
The base material is an impact-resistant acrylic resin having a particle size of m and discontinuously dispersed by 5 to 70% by weight, and the general acrylic resin having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms is used as a laminate. 0.5μ on one or both sides of the material
Optical properties with a haze value of 1.0% or less and a gloss of 130% or more when laminated with a thickness of m to 100μm and a total thickness of the laminated portion within 30% of the thickness of the entire sheet Impact-resistant acrylic resin laminated sheet with excellent weather resistance. 2. The general acrylic resin layer is a copolymer layer of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and an alkyl acrylate having an alkyl group having 1 to 4 carbon atoms within 20% by weight. The impact-resistant acrylic resin laminated sheet according to claim 1, wherein