AU762952B2

AU762952B2 - Method for producing multi-layer resin molded article

Info

Publication number: AU762952B2
Application number: AU30116/00A
Authority: AU
Inventors: Satoru Funakoshi; Koji Ogura; Hachiro Yamada
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 1999-04-27
Filing date: 2000-04-26
Publication date: 2003-07-10
Anticipated expiration: 2020-04-26
Also published as: TW486421B; NZ504028A; AU3011600A; KR20000071799A

Description

S&F Ref: 504350

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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Name and Address of Applicant: Actual Inventor(s): Address for Service: Sumitomo Chemical Company, Limited 5-33, Kitahama 4-Chome Chuo-ku Osaka 541-8550 Japan Koji Ogura, Satoru Funakoshi, Hachiro Yamada Spruson Ferguson St Martins Tower 31 Market Street Sydney NSW 2000 Method-for Producing Multi-layer Resin Molded Article Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c METHOD FOR PRODUCING MULTI-LAYER RESIN MOLDED ARTICLE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for producing a multi-layer thermoplastic resin molded article.

Particularly, the present invention relates to a method for producing a multi-layer thermoplastic resin molded article having almost no drug line.

i0 Description of the Related Art S"Conventionally, molded articles comprising :thermoplastic resins are widely known, and used widely also as sanitary articles such as bath tub, wash stands and the like, for example.

"Such thermoplastic resin molded article carries surfaces which are watched directly by users and come in contact with skins of users, and there are generally selected and used thermoplastic resins such as acrylic resins and the like having excellent appearance, feeling and the like.

However, such resins may inferior in strength, therefore, are often reinforced by other resin layer provided on the rear surface.

As the method for producing a multi-layer thermoplastic resin molded article having a resin layer for reinforcement 1 on the rear surface, there is known, for example, a method for heat-molding a multi-layer thermoplastic resin plate carrying two or more thermoplastic resin layers laminated.

According to this method, a multi-layer thermoplastic resin molded article having intended form is produced by heating a multi-layer thermoplastic resin plate to soften all thermoplastic resins constituting the multi-layer thermoplastic resin plate, then, shaping the plate using a *mold. For heating, a circulation furnace-type heater and 10 the like are usually used.

*,,,*However, when such a multi-layer thermoplastic resin plate is heated for shaping at temperatures higher than the temperature at which all thermoplastic resins constituting the plate are soften, unevenness in thickness called drug S 15 line has been sometimes recognized. Occurrence of such unevenness in thickness on the surface layer is particularly disadvantageous for uses including sanitary articles significantly requiring excellent appearance, feeling and the like.

For obtaining a multi-layer thermoplastic resin molded article having almost no drug line, the heating temperature may advantageously be decreased in some cases, however, since some thermoplastic resins constituting the multi-layer thermoplastic resin plate are not fully softened, a molded article having intended form can not be obtained easily.

2 SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for producing a multi-layer thermoplastic resin molded article having almost no drug line by heatmolding a multi-layer thermoplastic resin plate.

The present inventors have intensively studied to develop a method for producing a multi-layer thermplastic resin molded article having almost no drug line by heatmolding, and resultantly found that drug line tends to occur .ooooi when, of layers constituting the multi-layer thermoplastic I.resin plate, a dynamic modulus(G'l) of a first surface layer Sand a dynamic modulus(G'2) of a second surface layer are in specific relation, and that a molded article having excellent molding property and having almost no drug line can be produced if a multi-layer thermoplastic resin plate comprising a first surface layer and a second surface layer in which the dynamic modulus(G'l) of the first surface layer and the dynamic modulus(G'2) of the second surface layer having in specific relation is used, and both of the first surface layer and the second surface layer of the multilayer thermoplastic resin plate are heated at different temperatures so that the ratio(G'i/G'2) of the dynamic modulus(G'l) of the first surface layer to the dynamic modulus(G'2) of the second surface layer is specific value, completing the present invention.

3 4 The present invention provides a method for producing a multi-layer thermoplastic resin molded article by heat-molding a multi-layer thermoplastic resin plate comprising a first surface layer and a second surface layer in which the dynamic modulus of the second surface layer is less than 1 x 10 5 Pa at temperatures at which the dynamic modulus (G'I1) of the first surface layer is not more than 5 x 105 Pa, wherein the first surface layer and the second surface layer of the multi-layer thermoplastic resin plate are heated and heat-molded at different temperatures so that the ratio 1/G'2) of the dynamic modulus 1) of the first surface layer to the dynamic modulus of the second surface layer is from 0.35 to 2.8, and wherein the dynamic moduli of the first surface layer and the ,o second surface layer of the multi-layer thermoplastic resin plate in heated condition are determined depending on the heating temperature by using the calibration line which is previously prepared by measuring the dynamic modulus at each temperature of thermoplastic resins constituting the layers.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawings The present invention will become more fully [R:LIBXX]0421 I.doc:KOB understood from the detailed description given herein below and accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein; Fig. 1 is a schematic sectional view of a multi-layer thermoplastic resin plate applied in the production method of the present invention.

Fig. 2 is a view showing heating pattern of a heater in Example i.

ooooo 10 Fig. 3 is a view showing measuring sites of the temperatures of a multi-layer thermoplastic resin plate.

S. Fig. 4 is a view showing a section of the bath tub [.obtained in Example i.

a Fig. 5 is a view showing thickness from hand rail part to side wall parts of the bath tub obtained in Example i.

Fig. 6 is a view showing the heating pattern of the heater in Comparative Example i.

Fig. 7 is a view showing thickness from handrail part to side wall parts of the bath tub obtained in Comparative Example i.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 is a schematic sectional view of a multi-layer thermoplastic resin plate(3) applied in the production method of the present invention, which has two surface layers(l,2) on the front surface and the rear surface.

The materials of the both surface layers(l,2) on the multi-layer thermoplastic resin plate are not particularly restricted if they are thermoplastic resins which can be thermoformed, and examples thereof include acrylic resins, acrylonitrile-butadiene-styrene copolymer(ABS), polyolef in-based resins such as polyethylene, polypropylene and the like. An acrylic resin having a weight average molecular of more than 500,000 and an acrylic resin having 10 cross-linked structure in at least one part of the resin are -preferably used as the material of the first surface layer(1).

These thermoplastic resins may also contain coloring agents, releasing agent, heat stabilizers, ultraviolet absorbers, antioxidants, inorganic fillers such as talc, glass fiber and the like.

Specifically, when a multi-layer thermoplastic resin molded article such as a bath tub, washing stand and the like is produced, the surface layer on the front side of the multi-layer thermoplastic resin molded article which is often watched and touched with skins can be made of a transparent acrylic resin and the surface layer on the rear side can be made of a colored ABS resin and the like, to provide excellent transparency and sufficient strength.

Such thermoplastic resin may also be cross-linked to 6 such extent as to cause thermoforming, and when, for example, a layer composed of a partially cross-linked acrylic resin is used as the surface layer on the front side of a sanitary article, namely as the first surface layer(l), a merit is preferably obtained that durability against hot water of about 90C can be improved. In this case, as the surface layer on the rear side of a sanitary article, namely as the second surface layer(2), a layer composed of, for example, an ABS resin is preferable due to adhesion strength with the S 10 first surface layer.

The dynamic modulus of such thermoplastic resin varies depending on the kind, polymerization degree, extent of cross-linking and the like of a resin used.

The thickness of the multi-layer thermoplastic resin 15 plate(3) is usually from about 1 to 20 mm. The ratio (dl:d2) of the thickness(dl) of the first surface layer(1) to the thickness(d2) of the second surface layer(2) is usually from 1:9 to 9:1.

The multi-layer thermoplastic resin plate(3) applied in the production method of the present invention is required to be a plate in which the dynamic modulus(G'2) of the second surface layer(2) is less than 1X10 5 Pa at temperatures at which the dynamic modulus(G' 1) of the first surface layer(1) is not more than 5X10 5 Pa. When the dynamic modulus(G'2) of the second surface layer at such temperatures is more than 7 X 10 5 Pa, occurrence of drug line is originally few.

Such multi-layer thermoplastic resin plate(3) can be easily produced by, for example, a method in which a thermoplastic resin plate constituting the first surface layer(l) and a thermoplastic resin plate constituting the second surface layer(2) are heat-pressed, a method in which a thermoplastic resin plate constituting the second surface layer is extruded and laminated on a thermoplastic resin plate constituting the first surface layer, as well as other methods.

o. ~In the present invention, such multi-layer thermoplastic resinplate(3) is heated and thermoformed, and in this heating, it is necessary to heat the first surface layer(l) and the second surface layer(2) at different 15 temperatures so that the ratio(G'1/G'2) of the dynamic modulus(G'l) of the first surface layer(l) to the dynamic modulus(G'2) of the second surface layer(2) is from 0.35 to 2.8, preferably from 0.37 to 2.0, further preferably from 0.39 to 1.5. When this ratio is less than 0.35 or more than 2.8, the drug line tends to occur.

The dynamic moduli(G'1,G'2) of both surface layers(l,2) in heated condition may be obtained by, for example, previously measuring the dynamic modulus at each temperature of thermoplastic resins constituting the layers to prepare a calibration line and determining depending on 8 the heating temperature by the calibration line. Any of dynamic moduli(G'l, G'2) can be measured by a usual method, for example, a method using a rheometer [see, "Lecture Rheology" (edited by Japanese Rheology Society), pp. 36 to 37, pp. 47 to 52, and the like].

For heating the multi-layer thermoplastic resin plate to satisfy the above-described ratio(G'1/G'2) of both surface layers(l,2), it may be advantageous, for example, to heat the first surface layer(1) side and the second surface S 10 layer(2) side by separate heaters having different heating temperatures. The heater temperature can be controlled by controlling the heater output when an electric heater is used as the heater.

Regarding extent of heating, it is preferable that the 15 dynamic modulus(G'l) of the first surface layer(l) is 1X 10 5 Pa or more and 2X10 6 Pa or less, preferably 1X10 6 Pa or less, and the dynamic modulus(G'2) of the second surface layer(2) is X105 Pa ormoreand2X106 Paorless, preferably 1X10 6 Pa or less, from the standpoint of molding property.

In heating, it is not necessary that the heating temperature of the whole area of the first surface layer or the second surface layer is the same. The heating temperature may be partially changed depending on the form of the intended molded article providing both surface layers(l,2) satisfy the dynamic moduli G'2) defined 9 in the present invention. For example, when a bath tub is produced, it is also possible to lower the heating temperature of parts corresponding to four corner portions at the bottom surface which are most easily expanded to reduce thickness.

The heated multi-layer thermoplastic resin plate is thermoformed while maintaining heating condition. The thermoforming may be vacuum molding or pressed molding, and can be conducted according to an ordinary method.

ooooo 1 0 The production method of the present invention is optimal as a method for producing sanitary articles which 00 *0 Sare watched by person and come in contact with skins since even a multi-layer thermoplastic resin molded article having almost no drug line can be produced with excellent shaping 15 property according to this method.

Examples The following examples further illustrate the present invention in detail below, but do not limit the scope of the present invention.

Example 1 Amulti-layer thermoplastic resinplate(3) [thickness: 12 mm, width: 1515 mm, length: 985 mm] having a first surface layer(1) composed of a partially cross-linked acrylic resin [thickness: 5 mm, dynamic modulus at 200'C 2.62X10 5 Pa] 10 laminated and a second surface layer(2) composed of an ABS resin [thickness: 7 mm, dynamic modulus(G'2) at 200C 0.60 5 Pa] laminated was fixed to a clamp frame of a vacuum molding machine( manufactured by Fuse Vacuum Co.,Ltd.

"CUPF1015-PWB"), and heated by a pair of electric heaters placed above and below the clamp frame [far infrared heater panels of 120 mmX120 mm (manufactured by Elestein-Werk Steinmetz, "HFS", 400 W (200 arranged longitudinally in 7 pieces at an interval of 150 mm and laterally in 10 pieces 10 at an interval of 150 mm, 70 pieces in total]. The multi-layer thermoplastic resin plate was placed so that the first surface layer(1) faced upward, and on the first surface layer(1) side, the heater was disposed at an interval of 165 mm from the first surface layer(1) and heating was conducted 15 so that the far infrared heater panels constituting the heater showed temperature distribution as shown in (a)part of Fig. 2. While on the second surface layer(2) side, the heater was disposed below the second surface layer at an interval of 210 mm from the second surface layer(2) and heating was conducted so that the far infrared heater panels constituting the heater showed temperature distribution as shown in (b)part of Fig. 2. The heating time was 883 seconds.

The temperature of the first surface layer(l) on the position indicated by in Fig. 3 of the multi-layer thermoplastic resin plate(3) directly after heating was 11 192C, and the temperature of the second surface layer(2) on the same position was 136 0 C. A calibration line showing the relation between the dynamic moludi(G'l, G'2) and the temperatures previously made for the surface layers(1,2) indicated a dynamic modulus of the first surface layer(l) of 3.05X10 5 Pa and a dynamic modulus of the second surface layer(2) of 7.60X10 5 Pa. The ratio of the dynamic modulus of the first surface layer to the dynamic modulus of the second surface layer was 0.40.

10 Next, the heater was removed out of the system, this heated multi-layer thermoplastic resin plate(3) was Simmediately subjected to vacuum molding using a mold for vacuum molding [in the form of bath tub, internal size; width of 1190 mm, length of 545 mm and maximum depth of 470 mm], S 15 to obtain a bath tub having the front surface composed of an acrylic resin and the rear surface composed of an ABS resin as shown in Fig. 4.

This bath tub(4) showed no drug line around whole periphery on the side wall parts(6) pending approximately perpendicular from the hand rail The thickness of the first surface layer (acrylic resin layer) and the second surface layer (ABS resin layer) (2) along from the hand rail part(5) to the side wall parts(6) of this bath tub measured at an interval of 1 cm were shown in Fig. 5. In Fig. 5, marks B, C, D, E and F indicate parts 12 corresponding to B, C, D, E and F in Fig. 4, respectively.

As shown in Fig. 5, in the resulted bath tub, the whole thickness changes from the part D through the part E to the part F.

Example 2 Heating was conducted in the same operation as in Example 1 except that the heating time was 686 seconds. The temperature of the first surface layer(l) on the position indicated by in Fig. 3 of the multi-layer thermoplastic

S

resin plate(3) directly after heating was 178 0 C, and the temperature of the second surface layer(2) on the same position was 130 0 C. A calibration line showing the relation between the dynamic moludi(G'1, G'2) and the temperatures previously made for the surface layers(l,2) indicated a 15 dynamic modulus(G'l) of the first surface layer(1) of 3.83 *X 10 s Pa and a dynamic modulus of the second surface layer.

of 10.3X10 5 Pa. The ratio of the dynamic modulus of the first surface layer to the dynamic modulus of the second surface layer was 0.37.

Next, vacuum molding was conducted in the same manner as in Example 1, to obtain a bath tub having the front surface composed of an acrylic resin and the rear surface composed of an ABS resin as shown in Fig. 4.

This bath tub(4) showed almost no drug line on the side wall parts(6) pending approximately perpendicular from the 13 hand rail Comparative Example 1 The same multi-layer thermoplastic resin plate(3) as used in Example 1 was used and heating was conducted in the same operation as in Example 1, except that the far infrared heater panels of the heater disposed at an interval of 165 mm from the first surface layer(l) were heated to cause the temperature distribution as shown in (a)part of Fig. 6, and the far infrared heater panels of the heater disposed at an 10 interval of 210 mm from the second surface layer(2) were heated to cause the temperature distribution as shown in (b)part of Fig. 6, and the heating time was 740 seconds. The temperature of the first surface layer(l) on the position ee indicated by in Fig. 3 of the multi-layer thermoplastic 15 resin plate(3) directly after heating was 200C, and the .temperature of the second surface layer(2) on the same position was 200°C. A calibration line showing the relation between the dynamic moludi(G'l, G'2) and the temperatures previously made for the surface layers(l,2) indicated a dynamic modulus(G'l) of the first surface layer(l) of 2.62 5 Pa and a dynamic modulus of the second surface layer(2) of 0.60X10 5 Pa. The ratio of the dynamic modulus(G'l) of the first surface layer to the dynamic modulus(G'2) of the second surface layer was 4.37.

Next, vacuum molding was conducted in the same manner 14 as in Example i, to obtain a bath tub having the front surface composed of an acrylic resin and the rear surface composed of an ABS resin.

This bath tub(4) showed drug line around whole periphery on part pending approximately 5 cm below from the hand rail part(5), of side wall parts(6) pending approximately perpendicular from the hand rail The thickness of the first surface layer (acrylic resin layer) and the second surface layer (ABS resin layer) (2) along from the hand rail part(5) to the side wall parts(6) .of this bath tub measured at an interval of 1 cm were shown in Fig. 7. In Fig. 7, marks B, C, D, E and F indicate parts corresponding to B, C, D, E and F in Fig. 4, respectively.

As shown in Fig. 7, in the resulted bath tub, the whole 15 thickness decreases from the part D to the part E, the whole thickness increases from the part E to the part F and the part E is in the form of concave. Such parts having decreased thickness and in the form of concave occurs along-whole periphery of the bath tub and called drug line.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the sprit and scope of the invention, and such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

15

Claims

1. A method for producing a multi-layer thermoplastic resin molded article by heat-molding a multi-layer thermoplastic resin plate comprising a first surface layer and a second surface layer in which a dynamic modulus of the second surface layer is less than 1 x 10 5 Pa at temperatures at which a dynamic modulus of the first surface layer is not more than 5 x 105 Pa, wherein the first surface layer and the second surface layer of the multi-layer thermoplastic resin plate are heated and heat-molded at different temperatures so that the ratio 1/G'2) of the dynamic modulus of the first surface layer to the dynamic modulus of the second surface layer is from 0.35 to 2.8, and wherein the dynamic moduli of the first surface layer and the second surface layer of the multi-layer thermoplastic resin plate in heated condition are determined depending on the heating temperature by using the calibration line which is previously prepared by measuring the dynamic modulus at each temperature of thermoplastic resins constituting the layers.

2. The method according to claim 1, wherein the first surface layer comprises a partially cross-linked acrylic resin.

3. The method according to claim 1, wherein the second surface layer comprises an acrylonitrile-butadiene-styrene copolymer.

4. The method according to claim 1, wherein the multi-layer thermoplastic resin mold article is a sanitary article.

A method for producing a multi-layer thermoplastic resin molded article substantially as hereinbefore described with reference to any one of the examples but excluding the comparative examples.

6. A multi-layer thermoplastic resin molded article whenever prepared by the 25 method according to any one of claims 1 to Dated 16 May, 2003 Sumitomo Chemical Company Limited Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [R:\UBXX]042 l.doc: KOB