JP2001353828A - Decorative sheet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To use a material other than vinyl chloride resin in addition to moderate flexibility, abrasion resistance, scratch resistance, chemical resistance, post-processability and 9
Provided is a decorative sheet having a heat resistance of 0 ° C. or higher and excellent in design. A base sheet 1 made of a non-vinyl chloride-based material is provided.
A decorative sheet having on its surface a polypropylene resin layer 5 of a homopolypropylene resin or a random polypropylene resin modified with an unsaturated carboxylic acid or an anhydride thereof, wherein the polypropylene resin layer 5 of the homopolypropylene resin comprises The surface of the sheet 1 is provided with an adhesive resin layer 4 made of a random polypropylene resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to wood-based boards,
The present invention relates to a decorative sheet to be used as a decorative board by bonding to a surface of an inorganic board, a metal plate or the like with an adhesive.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride resin sheets have been most commonly used as decorative sheets used for the decorative boards. However, in recent years, vinyl chloride resin has become a factor in the generation of hydrogen chloride gas and dioxin, which is a highly toxic substance, causing acid rain during incineration, and the problem of bleeding out of plasticizers added to vinyl chloride resin sheets. There was also a problem from the viewpoint of environmental protection. Under such circumstances, a decorative sheet using a resin instead of the vinyl chloride resin has been demanded.

[0003] Accordingly, decorative sheets using resins and copolymers such as polyethylene, polypropylene, polyethylene terephthalate, ethylene-vinyl alcohol, and acrylic as alternative resins to vinyl chloride resin have been proposed.

[0004] Among them, cosmetics using polypropylene which are provided with moderate flexibility required for a decorative sheet, abrasion resistance, scratch resistance, heat resistance, chemical resistance, post-processability and the like and are provided at a low cost. Many seats have been proposed. Some of them have a single layer, but most of them are composed of a laminate of two or more layers because design is also important.

[0005] Since the polypropylene resin is a resin having poor adhesion to the same or different kinds of resins, when laminating a polypropylene resin layer on another resin layer, for example, maleic acid-modified polyethylene resin or ethylene- ( It is common to laminate via an adhesive resin layer such as a (meth) acrylic acid copolymer resin.

In recent years, there has been a great demand for not only a decorative sheet using a resin other than a vinyl chloride resin but also a further improvement in required physical properties. One of them is the further improvement of heat resistance. In the current decorative sheet, when the surface temperature and the ambient temperature are 90 ° C. or more, the laminate strength is significantly reduced.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to use a material other than a vinyl chloride resin to provide a moderately flexible material. An object of the present invention is to provide a decorative sheet having heat resistance of 90 ° C. or more in addition to heat resistance, abrasion resistance, scratch resistance, chemical resistance, and post-processability, and also having excellent design properties.

[0008]

According to a first aspect of the present invention for achieving the above object, a substrate sheet made of a non-vinyl chloride material is modified with an unsaturated carboxylic acid or an anhydride thereof. A decorative sheet comprising a polypropylene resin layer made of a random polypropylene resin.

Next, according to a second aspect of the present invention, in the decorative sheet according to the first aspect, the polypropylene resin layer is laminated on the surface of the base sheet by hot melt extrusion. It is a decorative sheet characterized by the above.

Next, the invention according to claim 3 of the present invention is to provide an adhesive resin layer made of a random polypropylene resin modified with an unsaturated carboxylic acid or its anhydride on the surface of a base sheet made of a non-vinyl chloride material. A decorative sheet comprising a polypropylene resin layer.

Next, the invention according to a fourth aspect of the present invention is the decorative sheet according to the third aspect of the present invention, wherein the adhesive resin layer and the polypropylene resin layer are co-extruded by heating and melting. It is a decorative sheet characterized by being laminated on the surface.

Next, the invention according to claim 5 of the present invention provides the decorative sheet according to any one of claims 1 to 4, wherein the unsaturated carboxylic acid or an anhydride thereof is a maleic anhydride. It is a decorative sheet characterized by being an acid.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1, 2 and 3 show examples of sectional views of a decorative sheet according to the present invention.

The basic structure of the decorative sheet according to the first and second aspects of the present invention is, as shown in FIG. 1, a base sheet 1 for a decorative sheet made of a non-vinyl chloride-based material.
It comprises a laminate with a transparent polypropylene resin layer 5 composed of a random polypropylene resin modified with an unsaturated carboxylic acid or its anhydride.

The basic structure of the decorative sheet according to the third and fourth aspects of the present invention is as shown in FIGS. 2 and 3, wherein the base sheet 1 for a decorative sheet is made of a non-vinyl chloride-based material.
And an adhesive resin layer 4 made of a random polypropylene resin modified with an unsaturated carboxylic acid or an anhydride thereof (for example, a random polypropylene resin graft-polymerized with maleic anhydride) as an intermediate adhesive layer for decorative sheet lamination.
And a transparent polypropylene resin layer 5 using at least one of a non-modified polypropylene resin or a random polypropylene resin modified in the same manner as the resin layer on the surface of the decorative sheet.

In the decorative sheet according to the third and fourth aspects of the present invention, the transparent polypropylene resin layer 5
As shown in FIG. 2 and FIG. 3, the polypropylene resin used for the adhesive is a random polypropylene resin modified with an unsaturated carboxylic acid or an anhydride thereof as an intermediate layer between the base sheet 1 and the polypropylene resin layer 5. Since the resin layer 4 is laminated, there is no need to use a modified random polypropylene resin, and there is no particular limitation. In the decorative sheet of the invention according to claim 3, as the polypropylene resin used for the transparent polypropylene resin layer 5, for example, if scratch resistance is important, a homopolypropylene having a high pentad fraction may be used; If V-cut suitability is emphasized, random polypropylene having a high ethylene content may be used. If necessary, a heat stabilizer, a flame retardant, an ultraviolet absorber, a light stabilizer, an antiblocking agent, a catalyst supplement, and the like are added.

According to the first, second and third aspects of the present invention,
In the decorative sheets of the inventions according to the inventions 4 and 5, the resin used for the base sheet 1 is preferably a non-vinyl chloride resin material such as a polypropylene resin or a random polypropylene resin, but is not necessarily limited thereto. For example, polyethylene, ethylene vinyl acetate copolymer, ethylene vinyl alcohol copolymer, polystyrene, ABS, polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, for example, , Polyvinyl acetal, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyurethane, polyamide, nylon 6,
Nylon 66 and the like.

In the resin used for the base sheet 1, one or more additives such as inorganic pigments, antioxidants, light stabilizers and antiblocking agents are added in appropriate amounts. Is possible.

In the decorative sheet according to the first, second, third, fourth, and fifth aspects of the present invention, the base sheet may have, for example,
In addition, a base sheet made of a non-vinyl chloride-based material concealed can be used.

The reason why the base sheet 1 is provided with the concealing property is to prevent a base material such as a wood board, an inorganic board and a metal plate to be bonded from being seen from the surface of the decorative sheet.

In order to prevent the woody board, the inorganic board, the metal plate and the like (base material) to be bonded to the base sheet 1 of the decorative sheet of the present invention from being seen from the surface of the decorative sheet, the base sheet is required. It is desirable that the base sheet 1 of the decorative sheet and the intermediate layer thereof be provided with concealing properties by adding pigment or forming a pigment coating layer (concealing layer). However, this is not always the case when it is desired to utilize the texture of the base material.

The method of forming the concealing property (concealing layer) and the pattern layer 2 on the base sheet 1 is as follows.
Gravure printing, intaglio printing, flexo printing, silk printing,
Printing is generally performed by a known printing method such as electrostatic printing or inkjet printing, but is not necessarily limited to this. The ink used is also a known one, that is, a coloring agent such as a dye or a pigment or an extender is added to a vehicle, and further, a plasticizer, a stabilizer, a wax, a grease, a drying agent, a curing agent, a thickener, a dispersant. And an ink obtained by arbitrarily adding a filler, etc., and kneading with a solvent, a diluent or the like.

A masking layer and / or a pattern layer 2 or both are formed on an arbitrary transfer base sheet different from the base sheet 1 for a decorative sheet by the above-described forming method and the like. After laminating with the base sheet 1 by a heat laminating method, a dry laminating method, a wet laminating method, an extrusion laminating method, or the like described in detail,
A method in which the transfer base sheet is peeled off and the concealing layer and / or the pattern layer 2 or both are transferred to the base sheet 1 can also be used.

When the T-die extrusion method is used as a method for manufacturing the base sheet 1, a synthetic resin material for forming the base sheet 1 is directly coated with a colorant having a masking property such as a dye or a pigment. By extruding from the T-die in a colored and heated and molten state to form the base sheet 1, the effect of concealment can be imparted.

In this case, as a method of coloring the base sheet 1 in the T-die extrusion method, a fine powder colorant obtained by treating a pigment with a dispersing aid or a surfactant is used to form the base sheet 1 into a film. Dry color method used by directly mixing into an uncolored ordinary synthetic resin material, or melting an uncolored ordinary synthetic resin material and a high-concentration pigment for forming the base sheet 1 into a film. The master batch pellets kneaded and pre-dispersed were prepared in advance, and in an extrusion hopper,
There is a master batch method or the like in which the master batch pellets and a non-colored ordinary synthetic resin material for forming the base sheet 1 are dry-blended.
There is no particular limitation.

The types of pigments may be those commonly used, but inorganic pigments such as titanium oxide, ultramarine blue, cadmium pigments, iron oxides, etc. are particularly desirable in view of heat resistance and weather resistance.
Further, among organic pigments, phthalocyanine pigments, quinacridone pigments and the like can be used. The ratio of the pigment to the resin and the color are appropriately determined in consideration of the degree of concealment and design, and are not particularly limited.

The method of applying the pattern layer 2 to the base sheet 1 includes a method of applying the pattern layer 2 to the surface of the base sheet 1 and a method of applying the pattern layer 2 to the base sheet 1 itself (in the layer of the sheet 1). The printing method and the transfer method as described above can be used. As a method for applying to the base sheet 1 itself, a high-concentration pigment is melt-kneaded with a resin having a different flow characteristic from the resin of the base sheet 1. Pre-dispersed master batch pellets, wood powder, glass powder, etc. are added to the above synthetic resin material having a concealing property for forming the base sheet 1 and heated and melted, extruded, and formed into a film. Then, there is also a method of forming a pattern using master batch pellets, wood powder, glass powder, or the like on the base sheet 1 itself having concealment properties. Of course, these methods of forming the color concealing property and the pattern on the base sheet 1 itself can be used in combination with the above-described printing method and transfer method.

In the case where the calender method is used as a method of manufacturing the base sheet 1 having the concealing property, the base sheet 1 itself is simultaneously colored while the base sheet 1 is manufactured by the calender method. The concealing property and the pattern can be formed on the base sheet 1 by a method of forming a concealing property or a pattern, or a method using these methods in combination with the above-described printing method, transfer method and the like.

In the decorative sheet according to the first, second, third, fourth and fifth aspects of the present invention, a transparent polypropylene resin layer is formed on the surface of the base sheet 1 having a hiding property. The reason for laminating 5 is to exhibit design properties, protection of the pattern layer, and scratch resistance, abrasion resistance, chemical resistance, and the like.

Lamination of the transparent base material sheet 1 and the transparent polypropylene resin layer 5 in the decorative sheet according to the first, second, third, fourth and fifth aspects of the present invention. As a method, a heat lamination method in which heat and pressure are applied for bonding, a dry lamination method and a wet lamination method in which bonding is performed via an adhesive, and an extrusion lamination method in which a polypropylene resin is melt-extruded from a T-die onto a base material sheet, There is a co-extrusion method in which a resin is melt-extruded from a T-die. Among them, the extrusion laminating method is preferably used because it has the highest productivity.

What matters here is the lamination strength of the base sheet 1 and the polypropylene resin layer 5. In particular,
In order to obtain sufficient strength in the decorative sheets according to the third and fourth aspects of the present invention shown in FIGS. 2 and 3, the anchor coat layer 3 is applied to the base sheet 1 (to which the pattern layer 2 is provided).
A method is known in which an adhesive resin layer 4 and a polypropylene resin layer 5 are co-extruded on the anchor coat layer 3 and an ozone gas is blown on the extruded resin to be the adhesive resin layer 4. is there.

The ozone treatment apparatus for blowing the ozone gas to the extruded resin to be the adhesive resin layer 4 may be a general one, and is not particularly limited. There are two types of ozone treatment: low-concentration, high-flow type and high-concentration, low-flow type. However, if the flow rate is too high, adverse effects such as film cracking of the molten resin and temperature drop can be considered. The ozone concentration is 20 to 50 g
/ Nm ^3, ozone flow rate 1~10Nm ³ / time is good.

Here, in order to make the laminate strength of the decorative sheet according to the first, second, third, fourth and fifth aspects of the present invention compatible with the laminate strength under normal temperature and high temperature. The present inventors have claimed in claims 1 and 2
The resin used for the transparent polypropylene resin layer 5 in the decorative sheet according to the invention according to the present invention and the resin used for the adhesive resin layer 4 in the decorative sheet according to the invention according to claims 3 and 4 are unsaturated carboxylic acids or anhydrides thereof. It has been found that a solution is obtained by using a modified random polypropylene resin (for example, a random polypropylene resin graft-polymerized with maleic anhydride).

That is, a polyethylene resin modified with an unsaturated carboxylic acid or an anhydride thereof (eg, a polyethylene resin graft-polymerized with maleic anhydride) has a high lamination strength at room temperature, but has a high lamination strength at high temperature, especially at 90 ° C. or higher. , Significantly lower. On the other hand, in the case of a homopolypropylene resin modified with an unsaturated carboxylic acid or an anhydride thereof (for example, a homopolypropylene resin graft-polymerized with maleic anhydride), the lamination strength does not decrease even when the temperature rises from room temperature to 100 ° C. Although not possible, the lamination strength itself at room temperature is low, and the suitability of the required lamination strength is not good. On the other hand, when the above random polypropylene resin modified with an unsaturated carboxylic acid or its anhydride is used, an appropriate lamination strength can be obtained, and from a room temperature to a high temperature of 100 ° C., a required stable lamination strength is obtained. can get.

Examples of the unsaturated carboxylic acid or its anhydride include acrylic acid, methacrylic acid, maleic acid, phthalic acid, citraconic acid, itaconic acid and their anhydrides. Among them, maleic anhydride is preferred. Particularly preferred. Further, the amount of these unsaturated carboxylic acids or anhydride units is preferably from 1 × 10 ^{−4 to} 1 × 10 ⁻¹ mmol equivalent as carbonyl groups per 1 g of the composition. If the amount of the unsaturated carboxylic acid or anhydride unit contained therein is less than 1 × 10 ^-4 milliequivalent, no sufficient effect is exhibited, and even if it is more than 1 × 10 ^-1 milliequivalent, the effect of improving the adhesiveness is not obtained. Becomes smaller.

Of course, when a random polypropylene is used for the polypropylene resin layer 5 as in the decorative sheet according to the first and second aspects of the present invention shown in FIG. If random polypropylene modified with an acid or its anhydride is used, even if the adhesive resin layer 4 used in the decorative sheet according to the third and fourth aspects of the invention is omitted, the object of the present invention (at room temperature) And maintenance of the laminate strength under high temperature) can be sufficiently achieved.

In the decorative sheet according to the first and second aspects of the present invention, between the laminate of the base sheet 1 and the polypropylene resin layer 5, or in the decorative sheet according to the third and fourth aspects. When the anchor coat layer 3 is used between the laminate of the material sheet 1 and the adhesive resin layer 4, the coating agent for the anchor coat layer 3 is not particularly limited in the present invention. A two-part curable urethane resin which forms a urethane bond by reacting with an isocyanate is preferable, and a resin containing at least one of 4,4-diphenylmethane diisocyanate and isophorone diisocyanate is preferable as the isocyanate. The method of forming the anchor coat layer 3 is preferably a gravure method (gravure printing method, gravure coating method), but is not limited thereto.

[0038] In the decorative sheet according to the first, second, third, fourth and fifth aspects of the present invention, the feel of the surface of the decorative sheet may be further improved in some cases. 1, 2 and 3, a concave pattern 5a is formed on a transparent polypropylene resin layer 5 on the surface of the decorative sheet, and a filling ink is embedded (wiped) in the concave portion. It is also preferable to provide a top coat layer 6 on the outermost surface of the polypropylene resin layer 5.

The method of forming the concave pattern 5a may be a normal hot-press embossing method, and is not limited at all. Also, a method for producing the polypropylene resin layer 5 (a single-layer extrusion film formation method for the polypropylene resin layer 5 or a two-layer co-extrusion film formation method for the base material sheet 1 and the polypropylene resin layer 5; When the T-die extrusion method is used as the two-layer co-extrusion film forming method with the resin layer 5, a projection pattern in which a concave pattern is inverted is applied to the surface of a chill roll for cooling and solidifying the molten resin, and the extruded resin is formed. Is embossed between the chill roll and the press roll,
In general, a method of forming a concave pattern 5a on the surface of the polypropylene resin layer 5 is used. It is also preferable to embed ink in the recessed portion of the applied recessed pattern 5a and to provide the top coat layer 6 on the outermost surface of the polypropylene resin layer 5, but these methods are based on a conventional vinyl chloride resin. It can be carried out in the same manner as the wiping process and the top coat process performed on the decorative sheet.

[0040]

EXAMPLES Hereinafter, a specific method for producing the decorative sheet of the present invention will be described.

Example 1 As shown in FIG. 1, as a base sheet 1, 6% by weight of an inorganic pigment, 0.2% by weight of a phenolic antioxidant, and a hindered amine light stabilizer were used in a random polypropylene resin. A sheet obtained by extruding a resin to which 0.3% by weight and an antiblocking agent are added by 0.2% by weight is subjected to a corona treatment on the sheet surface, and then a gravure printing method is applied to a pattern ink (Toyo Ink Manufacturing Co., Ltd. Co., Ltd .; Lamister) using a wood grain pattern,
The pattern layer 2 was formed. Furthermore, 2 on the wood-grain pattern layer 2
A liquid curing type urethane anchor coating agent was applied by a gravure printing method to form an anchor coat layer 3.

Next, the base sheet 1 provided with the pattern layer 2
A modified random polypropylene resin graft-polymerized with maleic anhydride (the carbonyl group content in 1 g of modified random polypropylene was
Phenolic antioxidant to 0.2
% By weight, 0.3% by weight of a hindered amine light stabilizer,
The embossed transparent polypropylene resin layer 5 having a concave pattern 5a on the surface to which 0.5% by weight of a benzotriazole type ultraviolet absorber and 0.2% by weight of an antiblocking agent are added.
Was laminated.

The recessed pattern 5 of the laminated body
A topcoat layer 6 was applied to the outermost surface of the transparent polypropylene resin layer 5 to which a was applied by using a urethane-based topcoat agent to obtain a decorative sheet of the present invention shown in FIG.

Example 2 As shown in FIGS. 2 and 3, as a base sheet 1, a random polypropylene resin was composed of 6% by weight of an inorganic pigment, 0.2% by weight of a phenolic antioxidant, and a hindered amine light. Using a sheet obtained by melt-extruding a resin containing 0.3% by weight of a stabilizer and 0.2% by weight of an anti-blocking agent, subjecting the sheet surface to a corona treatment, and then applying a gravure printing method to a pattern ink (TOYO A wood grain pattern was formed using Ink Manufacturing Co., Ltd. (Lamistar) to form a pattern layer 2. Further, a two-component curable urethane-based anchor coating agent was applied on the wood-grained pattern layer 2 by gravure printing to form an anchor coat layer 3.

Separately, as a transparent polypropylene resin layer 5, a homopolypropylene resin containing 0.2% by weight of a phenolic antioxidant, 0.3% by weight of a hindered amine light stabilizer and a benzotriazole type ultraviolet absorber was used. A resin to which 0.5% by weight and 0.2% by weight of an antiblocking agent are added, and a modified random polypropylene resin graft-polymerized with maleic anhydride as the adhesive resin layer 4 (the content of carbonyl group in 1 g of the modified random polypropylene is 0.1%). (2 mmol equivalent) between the cooling roll and the pressure roll on which the conduit is embossed, co-extrusion through the base sheet 1 from the T-die, and immediately before lamination with the base sheet 1 The surface of the co-extruded modified random polypropylene resin which becomes the adhesive resin layer 4 is treated with ozone gas by an ozone treatment apparatus. By spraying and simultaneously performing the lamination and the embossing, the embossed pattern 5a is formed on the surface of the anchor coat layer 3 on the base sheet 1 on which the pattern layer 2 is provided, with the adhesive resin layer 4 interposed therebetween. The laminated polypropylene resin layer 5 was laminated.

The concave pattern 5 of this laminated body
A topcoat layer 6 was applied to the outermost surface of the transparent polypropylene resin layer 5 to which a was applied by using a urethane-based topcoat agent to obtain a decorative sheet of the present invention shown in FIGS. 2 and 3.

<Comparative Example 1> The resin as the adhesive resin layer 4 to be co-extruded with the homopolypropylene resin as the transparent polypropylene resin layer 5 in the above Example 1 is a polyethylene resin graft-polymerized with maleic anhydride. Creates a decorative sheet in the same manner as in Example 1 above,
A decorative sheet of Comparative Example 1 was obtained.

<Comparative Example 2> The resin as the adhesive resin layer 4 to be coextruded with the homopolypropylene resin as the transparent polypropylene resin layer 5 in Example 1 is a homopolypropylene resin graft-polymerized with maleic anhydride. Otherwise, a decorative sheet was prepared in the same manner as in Example 1 to obtain a decorative sheet of Comparative Example 2.

<Comparison result> Thus, the above-mentioned Example 1 was obtained.
And 2, each of the decorative sheets obtained in Comparative Examples 1 and 2 was heated in a 23 ° C. atmosphere and at 80 ° C. for 120 hours, at 90 ° C. for 120 hours, and at 100 ° C. for 120 hours.
Measure the laminate strength in each condition of time heating,
The results are shown in Table 1 below.

[0050]

[Table 1]

[0051]

As described above, since the decorative sheet of the present invention does not use any vinyl chloride, there is no concern about environmental problems, and the decorative sheet has appropriate flexibility, abrasion resistance, scratch resistance, chemical resistance, and the like. In addition to the post-processability, it has excellent effects such as having heat resistance of 90 ° C. or more, and has the effect of providing a decorative sheet excellent in design.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an example of a decorative sheet according to the present invention.

FIG. 2 is a side sectional view showing another example of the decorative sheet according to the present invention.

FIG. 3 is a side sectional view showing another example of the decorative sheet according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base sheet 2 ... Pattern layer 3 ... Anchor coat layer
4: Adhesive resin layer 5: Polypropylene resin layer 5a: Depressed pattern 6: Top coat layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Ikeda 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. F-term in Toppan Printing Co., Ltd. (reference) 4F100 AA00 AK01C AK07B AK51 AL03B AL07B AT00A BA03 BA07 BA10A BA10B CA05 CA06 CA13 CA17 CA30 CB00C EH20 EJ42 GB08 JB01 JJ03 JK07 JK09 JK13

Claims (5)

[Claims] 1. A decorative sheet comprising a substrate sheet made of a non-vinyl chloride-based material and a polypropylene resin layer made of a random polypropylene resin modified with an unsaturated carboxylic acid or an anhydride thereof. 2. The decorative sheet according to claim 1, wherein the polypropylene resin layer is laminated on the surface of the base sheet by hot melt extrusion. 3. A substrate sheet comprising a non-vinyl chloride-based material, wherein a polypropylene resin layer is provided via an adhesive resin layer of a random polypropylene resin modified with an unsaturated carboxylic acid or an anhydride thereof. To make a decorative sheet. 4. The decorative sheet according to claim 3, wherein the adhesive resin layer and the polypropylene resin layer are laminated on the surface of the base sheet by hot melt coextrusion. 5. The decorative sheet according to claim 1, wherein said unsaturated carboxylic acid or anhydride thereof is maleic anhydride.