KR100694447B1 - Method for preparing thermoplastic resin having excellent moldability and chemical resistance and method for preparing thereof - Google Patents

Abstract

The present invention relates to a thermoplastic resin composition having excellent molding processability and chemical resistance, and a method for producing the same, in particular, having a weight average molecular weight of 200,000 to 400,000 consisting of a graft copolymer containing rubber-modified styrene, an aromatic vinyl compound, and an unsaturated nitrile monomer. Ultra low molecular weight copolymer resin having a weight average molecular weight of 50,000 to 150,000 consisting of a high molecular weight copolymer resin, an aromatic vinyl compound and an unsaturated nitrile monomer, and an ultra high molecular weight air having a weight average molecular weight of 1,000,000 to 3,000,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer. It is manufactured by mixing the copolymer resin in a certain ratio, and thus, the thermoplastic resin composition having excellent moldability and chemical resistance suitable for use in a refrigerator inner sheet because of excellent vacuum formability, extrusion stability, chemical resistance, processability, and fluidity, About to be.

Thermoplastic resin, block polymerization, suspension polymerization, emulsion polymerization, vacuum forming, chemical resistance

Description

Thermoplastic resin composition excellent in molding processability and chemical resistance and its manufacturing method {METHOD FOR PREPARING THERMOPLASTIC RESIN HAVING EXCELLENT MOLDABILITY AND CHEMICAL RESISTANCE AND METHOD FOR PREPARING THEREOF}

The present invention relates to a thermoplastic resin composition having excellent molding processability and chemical resistance, and a method of manufacturing the same, and more particularly, to be suitable for use in a refrigerator inner sheet because of excellent vacuum formability, extrusion stability, chemical resistance, processability, and flowability. The present invention relates to a thermoplastic resin composition excellent in molding processability and chemical resistance, and a manufacturing method thereof.

Generally, acrylonitrile-butadiene-styrene (ABS) resins have excellent mechanical and thermal properties due to properties such as styrene processability, stiffness and chemical resistance of acrylonitrile, and impact resistance of butadiene rubber. It has beautiful appearance characteristics and is widely used in electric, electronic housing, automobile interior and exterior materials, and the like.

Among them, the ABS resin used in the refrigerator inner sheet of the home appliance field, in addition to the above-mentioned properties, the three components of extrusion stability, vacuum forming, and chemical resistance must be properly balanced to obtain an excellent product as a refrigerator inner sheet.

In case of general ABS resin, due to the weak stretching property, there are many thickness variations for each part during vacuum molding, so that a thin part is formed locally. This thin part is formed by the residual stress and external impact during the assembly process and use of the refrigerator. Easily broken phenomenon has a problem.

As a conventional technique for increasing vacuum forming as described above, a method of introducing a copolymer composition of a vinyl cyan compound and an aromatic vinyl compound having an ultra high molecular weight or nonlinear structure into a rubber-reinforced styrene resin is mainly used. In particular, Korean Patent Application No. 2001-0083123 discloses a method of introducing a copolymer having ultra-high molecular weight of a nonlinear structure prepared by adding a multifunctional mercaptan and a polyfunctional acrylic monomer. This method can improve the vacuum formability of the final ABS resin, but there is a problem that productivity is lowered due to an increase in load during compounding and sheet extrusion due to the deterioration of fluidity.

In addition, in order to improve extrusion stability, it is important to minimize the deformation of rubber particles in the extrusion direction and the right angle direction of extrusion so as to have a constant thickness without variation in the thickness of the sheet. It is possible to minimize the defective phenomenon caused by the cause.

In order to solve the problems of the prior art as described above, the present invention provides a thermoplastic resin composition excellent in molding processability and chemical resistance that can significantly improve vacuum formability, extrusion stability, chemical resistance, processability, and flowability, and a manufacturing method thereof. The purpose is to.

Another object of the present invention is to provide a thermoplastic resin composition suitable for use in a refrigerator inner sheet and a method of manufacturing the same.

In order to achieve the above object, the present invention provides a thermoplastic resin composition excellent in molding processability and chemical resistance,

a) graft copolymer containing rubber modified styrene;

b) a high molecular weight copolymer resin having a weight average molecular weight of 200,000 to 400,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer;

c) a medium to low molecular weight copolymer resin having a weight average molecular weight of 50,000 to 150,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer; And

d) ultra high molecular weight copolymer resin having a weight average molecular weight of 1,000,000 to 3,000,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer

It comprises a, a: b + c = 20: 80 to 50: 50 is mixed in a weight ratio, b: c = 30: 70 to 70: 30 is mixed in a weight ratio, d is a + b + c 100 It provides a thermoplastic resin composition excellent in molding processability and chemical resistance, characterized in that contained in 0.1 to 20 parts by weight with respect to parts by weight.

In addition, the present invention is a method for producing a thermoplastic resin composition,

a) preparing a graft copolymer (a) containing rubber-modified styrene;

b) suspending and polymerizing the aromatic vinyl compound and the unsaturated nitrile monomer to prepare a high molecular weight copolymer resin (b) having a weight average molecular weight of 200,000 to 400,000;

c) bulk polymerization of an aromatic vinyl compound and an unsaturated nitrile monomer to prepare a low to medium molecular weight copolymer resin (c) having a weight average molecular weight of 50,000 to 150,000;

d) emulsion-polymerizing the aromatic vinyl compound and the unsaturated nitrile monomer to prepare an ultra high molecular weight copolymer resin (d) having a weight average molecular weight of 1,000,000 to 3,000,000; And

e) a), b), c) and d) are mixed in a weight ratio of a: b + c = 20: 80-50: 50 and b: c = 30: 70-70: 30 D is mixed so as to be 0.1 to 20 parts by weight based on 100 parts by weight of a + b + c.

It provides a method for producing a thermoplastic resin composition excellent in molding processability and chemical resistance comprising a.

Hereinafter, the present invention will be described in detail.

The thermoplastic resin composition having excellent molding processability and chemical resistance of the present invention is a high molecular weight copolymer having a weight average molecular weight of 200,000 to 400,000 consisting of a) a graft copolymer containing rubber-modified styrene, b) an aromatic vinyl compound and an unsaturated nitrile monomer. Medium to low molecular weight copolymer resins having a weight average molecular weight of 50,000 to 150,000 consisting of resins, c) aromatic vinyl compounds and unsaturated nitrile monomers, and d) ultra high molecular weight air having a weight average molecular weight of 1,000,000 to 3,000,000 consisting of aromatic vinyl compounds and unsaturated nitrile monomers. It comprises a copolymer resin, mixed in a weight ratio of a: b + c = 20:80 to 50:50, mixed in a weight ratio of b: c = 30:70 to 70:30, d is a + b + c is included in an amount of 0.1 to 20 parts by weight based on 100 parts by weight.

The graft copolymer containing the rubber modified styrene of a) used in the present invention may be prepared by polymerizing a monomer mixture of an aromatic vinyl compound and a vinyl cyan compound on a rubber latex.

Preferably, the rubber latex has an average particle diameter of 0.25 to 0.40 μm, and when the average particle diameter is less than 0.25 μm, the appearance and natural color of the final molded product are somewhat improved, but the impact strength is low due to the inefficiency of the rubber for imparting impact resistance. If it exceeds 0.40 ㎛, the impact resistance is somewhat increased, but the mechanical stability of the graft copolymer is deteriorated, excessive coagulation is generated, and the flowability and gloss of the final molded product is deteriorated. There is this.

As the rubber latex, butadiene, polybutadiene, styrene-butadiene, polyisoprene, or butadiene-isoprene copolymer may be used, and in particular, butadiene may be used.

The rubber latex is preferably included in 10 to 60 parts by weight based on 100 parts by weight of the total monomers used in the graft copolymer production.

As the aromatic vinyl compound, styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, substituted styrene of t-butyl styrene, or the like may be used, and styrene is particularly preferable. The aromatic vinyl compound may be included in an amount of 30 to 60 parts by weight based on 100 parts by weight of the total monomers used in preparing the graft copolymer.

As the vinyl cyan compound, acrylonitrile, methacrylonitrile, ethacrylonitrile, or the like can be used, and in particular, acrylonitrile is preferably used. The vinyl cyan compound may be included in an amount of 10 to 30 parts by weight based on 100 parts by weight of the total monomers used in preparing the graft copolymer.

In the polymerization reaction of the rubber latex and the monomer mixture as described above, an emulsifier, a molecular weight regulator, a polymerization initiator, and ion-exchanged water used in the manufacture of a conventional graft copolymer may be added.

The graft copolymer containing the rubber-modified styrene can be prepared by a conventional polymerization method, and in particular, it is preferable to polymerize by a bulk polymerization method or an emulsion polymerization method.

The high molecular weight copolymer resin of b) used in the present invention may be prepared by suspension polymerization of an aromatic vinyl compound and an unsaturated nitrile monomer.

The aromatic vinyl compound may use the same components as used in preparing the graft copolymer of a), and the content thereof is preferably used in an amount of 60 to 75 parts by weight based on 100 parts by weight of the high molecular weight copolymer resin.

As the unsaturated nitrile monomer, acrylonitrile, methacrylonitrile, or ethacrylonitrile may be used, and the content thereof is preferably used in an amount of 25 to 40 parts by weight based on 100 parts by weight of the high molecular weight copolymer resin.

In the suspension polymerization of the aromatic vinyl compound and the unsaturated nitrile monomer as described above, it is possible to add components such as water, a polymerization initiator, a molecular weight regulator, and the like, which are usually used during suspension polymerization.

The suspension polymerization can be carried out by a conventional method, specifically, 60 to 75 parts by weight of an aromatic vinyl compound and 25 to 40 parts by weight of an unsaturated nitrile monomer are added under a suspension polymerization stabilizer through water, and a half life of 10 hours is used as an initiator. It can superpose | polymerize by the conventional suspension polymerization method using the polyfunctional organic peroxide initiator whose temperature corresponds to 80-130 degreeC.

The high molecular weight copolymer resin of b) prepared as described above preferably has a weight average molecular weight of 200,000 to 400,000, and when the weight average molecular weight is less than 200,000, there is a problem that the vacuum forming of the sheet is lowered, and exceeds 400,000. In this case, there is a problem that the extrusion processability of the resin is lowered.

The low and medium molecular weight copolymer resin of c) used in the present invention may be prepared by bulk polymerization of an aromatic vinyl compound and an unsaturated nitrile monomer.

The aromatic vinyl compound and the unsaturated nitrile monomer may be used in the same amount as the same components used in the preparation of the high molecular weight copolymer resin of b).

In the case of bulk polymerization of the aromatic vinyl compound and the unsaturated nitrile monomer, it is possible to add components such as a polymerization initiator, a molecular weight regulator, and the like, which are usually used for bulk polymerization, and specifically, 60 to 75 parts by weight of an aromatic vinyl compound and an unsaturated nitrile. 25-40 weight part of monomers can be thrown, and it can superpose | polymerize by a conventional block polymerization method.

The medium and low molecular weight copolymer resin of c) prepared as described above preferably has a weight average molecular weight of 50,000 to 150,000, and when the weight average molecular weight is less than 50,000, there is a problem that the vacuum forming of the sheet is lowered, and exceeds 150,000. In this case, there is a problem that the extrusion processability of the resin is lowered.

The ultrahigh molecular weight copolymer resin of d) used in the present invention may be prepared by emulsion polymerization of an aromatic vinyl compound and an unsaturated nitrile monomer.

The aromatic vinyl compound and the unsaturated nitrile monomer may be used in the same amount as the same components used in the preparation of the high molecular weight copolymer resin of b).

In the emulsion polymerization of the aromatic vinyl compound and the unsaturated nitrile monomer, it is, of course, possible to add components such as an emulsifier, a polymerization initiator, a molecular weight regulator, and ion-exchanged water, which are usually used in the emulsion polymerization. Can be polymerized accordingly.

The ultra-high molecular weight copolymer resin of d) prepared as described above preferably has a weight average molecular weight of 1,000,000 to 3,000,000, more preferably 2,000,000. When the weight average molecular weight is less than 1,000,000, there is a problem that the vacuum forming improvement is low, when the weight average molecular weight is more than 3,000,000 there is a problem that the fluidity is significantly lowered and workability is lowered.

The thermoplastic resin composition of the present invention comprising the above components may be used in addition to the above components, such as antioxidants, lubricants, thermal stabilizers, light stabilizers, anti-dropping agents, pigments, or inorganic fillers, such as hindered phenolic or phosphite based compounds. Additives may further be used.

The thermoplastic resin composition of the present invention containing the above components can be mixed by a conventional blending method.

At this time, the graft copolymer containing the rubber-modified styrene of a): the sum of the high molecular weight copolymer resin of b) and the low to medium molecular weight copolymer resin of c) is mixed in a weight ratio of 20: 80 to 50: 50. Preferably, when the mixture is out of the weight range, there is a problem that the impact strength is lowered or the workability is lowered.

The high molecular weight copolymer resin of b) and the low to medium molecular weight copolymer resin of c) are preferably mixed in a weight ratio of 30:70 to 70:30, and when the mixture is out of the weight range, vacuum forming or processability There is a problem that this is lowered.

In addition, the ultra-high molecular weight copolymer resin of d) is 0.1 to a total of 100 parts by weight of the graft copolymer containing a) rubber modified styrene of + a) high molecular weight copolymer resin of b) + medium to low to medium molecular weight copolymer resin of c) It is preferable to include from 20 parts by weight, and if the content is less than 0.1 parts by weight or more than 20 parts by weight, there is a problem that the effect is insignificant or the workability is lowered.

In another aspect, the present invention provides a method for producing a thermoplastic resin composition as described above, the thermoplastic resin composition prepared according to the present invention significantly improves the vacuum formability, extrusion stability, chemical resistance, processability, and fluidity for the refrigerator inner sheet It is suitable for application to blowing agents of CFC-based, HCFC-based, or cyclopentane.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

EXAMPLE

Example 1

Graft copolymer containing rubber-modified styrene, g-ABS resin having a core-shell form prepared by emulsion polymerization of styrene and acrylonitrile on rubber latex having an average particle diameter of 0.3 µm (Part) 36 parts by weight of acrylonitrile content prepared by suspension polymerization, 32 parts by weight of a SAN resin B-1 (Lab polymerization) having a weight average molecular weight of 270,000, and 30% by weight acrylonitrile made by bulk polymerization, 30 parts by weight of a SAN resin having an average molecular weight of 130,000 (C-1, LG Chem) and an acrylonitrile content of 26% prepared by emulsion polymerization, and a SAN resin having a weight average molecular weight of 2,300,000 (D-1, LG Chemical Co., Ltd.) 1 part by weight of a blend to prepare a thermoplastic resin.

Examples 2-4 and Comparative Examples 1-7

A thermoplastic resin was prepared in the same manner as in Example 1, except that Example 1 was used as a component and a composition ratio shown in Table 1 below.

division Example Comparative example One 2 3 4 One 2 3 4 5 6 7 Graft copolymer ¹⁾ 34 34 34 34 34 34 34 34 34 34 34 High molecular weight copolymer resin B-1 ²⁾ 36 30 - - 30 18 - - - - - B-2 ³⁾ - - 36 30 - - 48 - - 66 - B-3 ⁴⁾ - - - - - - - 36 - - - Low to Medium Molecular Weight Copolymer Resin C-1 ⁵⁾ 30 36 30 36 36 48 18 30 - - 66 C-2 ⁶⁾ - - - - - - - - 66 - Ultra low molecular weight copolymer resin ⁷⁾ One One One One One One One One One One One 1: Rubber-Latex-containing g-ABS resin with an average particle diameter of 0.3 µm (GE Chemical Co., Ltd.) 2: SAN resin having an acrylonitrile content of 32% and a weight average molecular weight of 270,000 prepared by suspension polymerization (Lab (Polymerization) 3: SAN resin having 32% acrylonitrile content and 330,000 weight average molecular weight prepared by suspension polymerization (Lab polymerization) 4: 32% acrylonitrile content and 180,000 weight average molecular weight prepared by suspension polymerization. SAN resin (Lab polymerization) 5: SAN resin with 30% acrylonitrile content prepared by bulk polymerization and 130,000 weight average molecular weight (LG Chem. Co., Ltd.) 6: 34% acrylonitrile content produced by bulk polymerization Resin having a weight average molecular weight of 170,000 (LG Chem) 7: SAN resin having 26% acrylonitrile content and 2,300,000 weight average molecular weight prepared by emulsion polymerization

Using the thermoplastic resins prepared in Examples 1 to 4 and Comparative Examples 1 to 7, the high temperature tensile strength, chemical resistance, and fluidity were measured by the following method, and the results are shown in Table 2 below.

A) high temperature tensile strength-after injection of pellets of 100 mm × 100 mm × 3.2 mm using the thermoplastic resins prepared in Examples 1-4 and Comparative Examples 1-7, The specimen was cut so that the width of 15 mm, the total width of 15 mm, and the width of the measurement site were 6.5 mm. After holding the prepared specimen at a temperature of 150 ℃ for 15 minutes, the INSTRON model No. The high temperature tensile strength was measured using 4301. At this time, when the tensile strength is high, vacuum forming is excellent.

B) Chemical resistance-After injection molding in the same manner as a) to prepare a tensile specimen of 195 mm × 19 mm × 3 mm size, the specimen is fixed to each jig for each strain for evaluation of chemical resistance, and then cyclopentane After immersion for 2 minutes, the sample was taken out and left to stand for 1 minute, and the value of JIG of the strain which does not bend and crack was measured.

C) melt index-measured according to ASTM D1238 method.

division Example Comparative example One 2 3 4 One 2 3 4 5 6 7 High temperature tensile strength (㎏f / ㎠) 4.6 4.2 4.8 4.4 3.8 4.0 5.1 4.0 3.9 5.3 3.5 Chemical resistance (JIG value) 2.0 2.0 2.0 2.0 2.0 1.9 2.0 2.0 1.7 2.0 1.5 Fluidity (g / 10min) 4.2 4.5 4.0 4.2 5.2 5.1 2.5 5.3 5.2 0.7 0.7

Through Table 2, the high molecular weight SAN resin prepared by suspension polymerization, the low and medium molecular weight SAN resin prepared by bulk polymerization, and the ultra high molecular weight SAN resin prepared by emulsion polymerization were mixed in a predetermined ratio. It was confirmed that the thermoplastic resins of Examples 1 to 4 prepared were excellent in vacuum formability, chemical resistance, and flowability as compared with Comparative Examples 1 to 7.

On the other hand, Comparative Example 1, which does not use an ultra high molecular weight SAN resin, Comparative Example 2, which does not use a medium or low molecular weight SAN resin, and Comparative Example 4, which are prepared by suspension polymerization but use a low molecular weight SAN resin, have excellent fluidity. However, it was confirmed that the high temperature tensile strength was decreased, and in Comparative Example 3 without using a high molecular weight SAN resin, the high temperature tensile strength was increased but the fluidity was decreased. In addition, Comparative Examples 5 to 7 to which one type of SAN resin was applied could confirm that the high temperature tensile strength decreased or the fluidity or chemical resistance decreased.

According to the present invention, the vacuum forming property, the extrusion stability, the chemical resistance, the processability, and the fluidity of the thermoplastic resin are remarkably improved, and thus, the present invention is suitable for use in a refrigerator inner sheet.

Although only described in detail with respect to the described embodiments of the present invention, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical spirit of the present invention, it is natural that such variations and modifications belong to the appended claims. .

Claims (12)

In the thermoplastic resin composition excellent in molding processability and chemical resistance, a) graft copolymer containing rubber modified styrene; b) a high molecular weight copolymer resin having a weight average molecular weight of 200,000 to 400,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer; c) a medium to low molecular weight copolymer resin having a weight average molecular weight of 50,000 to 150,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer; And d) ultra high molecular weight copolymer resin having a weight average molecular weight of 1,000,000 to 3,000,000 consisting of an aromatic vinyl compound and an unsaturated nitrile monomer It comprises a, a: b + c = 20: 80 to 50: 50 is mixed in a weight ratio, b: c = 30: 70 to 70: 30 is mixed in a weight ratio, d is a + b + c 100 The thermoplastic resin composition excellent in molding processability and chemical resistance, characterized in that contained in 0.1 to 20 parts by weight with respect to parts by weight. The method of claim 1, The graft copolymer containing the rubber-modified styrene of a) Iii) 10 to 60 parts by weight of rubber latex selected from the group consisting of butadiene, polybutadiene, styrene-butadiene, polyisoprene, and butadiene-isoprene copolymer; Ii) 30 to 60 parts by weight of an aromatic vinyl compound selected from the group consisting of substituted styrenes of styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and t-butyl styrene; And Iii) 10 to 30 parts by weight of a vinyl cyan compound selected from the group consisting of acrylonitrile, methacrylonitrile, and ethacrylonitrile A thermoplastic resin composition excellent in molding processability and chemical resistance, characterized by being prepared by polymerization. The method of claim 2, The thermoplastic resin composition excellent in molding processability and chemical resistance, characterized in that the average particle diameter of the rubber latex of (i) is 0.25 to 0.40 µm. The method of claim 1, The thermoplastic resin composition having excellent moldability and chemical resistance, characterized in that the high molecular weight copolymer resin of b) is prepared by suspension polymerization of 60 to 75 parts by weight of an aromatic vinyl compound and 25 to 40 parts by weight of an unsaturated nitrile monomer. The method of claim 1, The thermoplastic resin composition having excellent molding processability and chemical resistance, characterized in that the low and medium molecular weight copolymer resin of c) is prepared by bulk polymerization of 60 to 75 parts by weight of an aromatic vinyl compound and 25 to 40 parts by weight of an unsaturated nitrile monomer. The method of claim 1, The thermoplastic resin composition having excellent molding processability and chemical resistance, wherein the ultra high molecular weight copolymer resin of d) is prepared by emulsion polymerization of 60 to 75 parts by weight of an aromatic vinyl compound and 25 to 40 parts by weight of an unsaturated nitrile monomer. The method according to any one of claims 4 to 6, The thermoplastic resin composition having excellent molding processability and chemical resistance, wherein the aromatic vinyl compound is selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and substituted styrene of t-butyl styrene. . The method according to any one of claims 4 to 6, The unsaturated nitrile monomer is at least one selected from the group consisting of acrylonitrile, methacrylonitrile, and ethacrylonitrile, thermoplastic resin composition excellent in molding processability and chemical resistance. The method of claim 1, The thermoplastic resin composition further comprises at least one additive selected from the group consisting of hindered phenol- or phosphite-based antioxidants, lubricants, heat stabilizers, light stabilizers, anti-drip agents, pigments, and inorganic fillers. A thermoplastic resin composition having excellent molding processability and chemical resistance. The method of claim 1, The thermoplastic resin composition is excellent in molding processability and chemical resistance, characterized in that the thermoplastic resin composition is applied to a refrigerator inner sheet. The method of claim 1, The thermoplastic resin composition is excellent in molding processability and chemical resistance, characterized in that the thermoplastic resin composition is applied to a blowing agent of CFC-based, HCFC-based, or cyclopentane. In the manufacturing method of the thermoplastic resin composition excellent in molding processability and chemical resistance, a) preparing a graft copolymer (a) containing rubber-modified styrene; b) suspending the aromatic vinyl compound and the unsaturated nitrile monomer to prepare a high molecular weight copolymer resin (b) having a weight average molecular weight of 200,000 to 400,000; c) bulk polymerization of an aromatic vinyl compound and an unsaturated nitrile monomer to prepare a low to medium molecular weight copolymer resin (c) having a weight average molecular weight of 50,000 to 150,000; d) emulsion-polymerizing the aromatic vinyl compound and the unsaturated nitrile monomer to prepare an ultra high molecular weight copolymer resin (d) having a weight average molecular weight of 1,000,000 to 3,000,000; And e) a), b), c) and d) are mixed in a weight ratio of a: b + c = 20: 80-50: 50 and b: c = 30: 70-70: 30 D is mixed so as to be 0.1 to 20 parts by weight based on 100 parts by weight of a + b + c. Method for producing a thermoplastic resin composition excellent in molding processability and chemical resistance comprising a.