JPH0532845A - Vibration-damping resin composition - Google Patents

Abstract

PURPOSE:To provide a thermoplastic resin compsn. which is excellent in vibration-damping properties, has a high stiffness, and is easily moldable. CONSTITUTION:A thermoplastic resin compsn. which has excellent vibration- damping properties and a high stiffness and which comprises a dispersed phase consisting of a thermoplastic polyurethane, pref. a polycarbonate-based one, and having a mean particle diameter of 0.01-10mum and a continuous phase consisting of a polymer of an alkyl alpha,beta-unsatd. carboxylate or, if necessary, a copolymer of the carboxylate with a copolymerizable monomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition which has excellent vibration damping properties, high steel properties, and can be easily molded.

[0002]

2. Description of the Related Art In recent years, environmental problems such as noise and vibration have come to the fore, and there is a demand for reduction of noise and vibration in the fields of automobiles, electric equipment and housing. For example, in the automobile field, damping materials are used or required for oil pans, head covers, dash panels, etc. around the engine, and in the electrical equipment field, solid transmission noise and vibration generated from a vibration source. Has become a problem, and reducing them has become one of the important performances. further,
In the fields of automobiles and information equipment, it is also desired to reduce the weight of the structure in order to save energy in addition to vibration control.

As the vibration damping material and the vibration damping material, it is desirable that the structure itself has a vibration damping property, but in general, a material having a high rigidity that can be a structure has a small vibration damping property, and conversely, a vibration damping property. Since the material having high properties has a trade-off relationship of low rigidity, it is difficult to use the resin composition having excellent vibration damping property as a structure as it is. As one of the means for overcoming this, Japanese Patent Laid-Open No. 54-4325
As disclosed in Japanese Patent Publication No. 1 and the like, there is a vibration-damping steel plate sandwiched by sandwiching a resin composition having excellent vibration-damping properties between two steel plates. However, in this vibration-damping steel plate, there is a large difference in heat shrinkage between the steel plate and the resin, so that poor adhesion occurs and the vibration-damping property deteriorates. Further, since it is a multi-layer composite material, the manufacturing process at the time of processing becomes complicated, and a large-scale composite device is required for processing. Furthermore, since the steel sheet itself has a large specific gravity, it is not preferable when it is desired to reduce the weight of the structure.

Further, as disclosed in Japanese Patent Application Laid-Open No. 55-153831, etc., in order to increase the rigidity of a resin material having excellent vibration damping properties but low rigidity, a filler such as glass filler or talc (main component is There is also a method of adding calcium carbonate). By this method, the rigidity of the resin is certainly improved, but new drawbacks such as low impact strength, large anisotropy of impact strength, and significant decrease in surface gloss are newly generated. Limited use. In addition, since the specific gravity increases due to the addition of the filler, it was not suitable for applications where weight reduction is required as in the case of damping steel plates.

Further, a thermoplastic elastomer such as polyurethane can be used as a material having a vibration damping property, but when used alone, its rigidity was insufficient to be used as a structure. Further, a composition of polyurethane and polymethacrylate is known in JP-A-53-148196, but the balance between vibration damping property and rigidity is not sufficient for use as a structure.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vibration-damping thermoplastic resin composition which has excellent vibration damping properties, high rigidity, and can be easily molded. is there.

[0007]

[Means for Solving the Problems] As a result of intensive studies made by the present inventors in order to solve the above problems, they have found means for solving the above problems. That is, the present invention relates to a copolymer comprising a thermoplastic polyurethane (I), an α, β-unsaturated carboxylic acid alkyl ester monomer (M), and a monomer (Y) copolymerizable therewith, if necessary. A vibration-damping resin composition comprising a polymer (II), a thermoplastic polyurethane (I) as a dispersion layer, and an average particle diameter of the dispersion layer in the range of 0.01 to 10 μm. is there.

The present invention will be described in more detail. When the thermoplastic polyurethane (I) and the copolymer (II) are blended, a sea-island structure is formed, and the average particle diameter of the thermoplastic polyurethane dispersion layer, which is an island, is 0.01 to 0.01 in terms of vibration damping property.
It is necessary to be in the range of 10 μm, and 0.01 to 5
The thickness is preferably in the range of μm, more preferably 0.01 to 1 μm. The average particle size of the dispersion layer is 10
If it exceeds 0.1 μm, the vibration damping property is deteriorated, and if it is less than 0.01 μm, the impact resistance is poor. The average particle size in the present invention is
The particle diameter of the dispersion layer is determined by an electron micrograph of an ultrathin section of the resin composition, and the particle diameter of the dispersion layer is represented by the arithmetic mean of the major axis and the minor axis of the dispersion layer.

The average particle size of the dispersion layer is 10 μm or less
As means for this, for example, shear stress during kneading,
Melt viscosity between polymers, interfacial tension between polymers,
The compatibility between the polymers can be utilized. To
The thermoplastic polyurethane (I) and the copolymer (I
I) is blended and kneaded with, for example, an extruder.
At this time, it is preferable that the shear stress be as high as possible.
Is 10³Pa or more, more preferably 10^FourPa or higher
And preferably 10⁶Pa or higher. for that purpose,
1) Increase the rotation speed of the extruder. 2) Extruder screen
In the clew pattern, the pattern that takes a share
You just have to select it, and in terms of screw parts, for example,
For example, seal ring, kneading disc L or Y
Do not use many screw parts with short pitches
It 3) It is possible to use means such as extrusion at a low temperature.
Wear. However, there is concern about heat deterioration of the resin due to shear heat generation.
In some cases, some restrictions may have to be
It The extrusion temperature is at least (I), or
It must be at a temperature at which (II) melts. Extruder
The shear stress when kneading with a
The same as the average particle size of the dispersion layer obtained by using a machine
Shear to obtain average particle size of dispersed layer by capillograph
It can be obtained as stress. About heat
Melt viscosity of plastic polyurethane (I) and copolymer (II)
The degree ratio is preferably in the range of 0.01 to 10,
More preferably, it is in the range of 0.05 to 5,
Consider the kneading temperature so that it is as close to 1 as possible.
Taking into consideration, select an appropriate combination of (I) and (II) and kneading temperature.
You can choose. As a means to measure melt viscosity
For example, a capillograph can be used.
For thermoplastic copolymers (I) and copolymers
The interfacial tension of the resin composition after blending with (II)
It is sufficient to lower the amount as much as possible. For example, a compatibilizer is also used.
You can As compatibilizer, polyurethane and
Block with α, β-unsaturated carboxylic acid alkyl ester
Copolymers and the like are effective, but are not limited to these.
Yes. For copolyester with thermoplastic polyurethane (I)
SP (Solubility Par) between united (II)
It is preferable that the value
The SP value of each resin is, for example, S
The formula of mall can be used. For example, thermoplastic
Polyurethane (I) 10.0cal^0.5/ Cm^1.5,
PMMA (polymethylmethacrylate) belonging to the copolymer (II)
Relate) resin is 9.3 cal ^0.5/ Cm^1.5And
It For example, copolymerizing PMMA with acrylonitrile
And increase the SP value by 10.0cal^0.5/ Cm^1.5To
You should be able to approach them.

As the thermoplastic polyurethane (I) in the present invention, those having a structure of polyester type, polyether type, polycaprolactone type, polycarbonate type (polycarbonate type) or the like can be used.
From the viewpoint of damping property after blending and high rigidity, a polycarbonate type is preferable. From the viewpoint of the balance between vibration damping performance and rigidity, hardness is defined by JIS K7311, JIS
A, preferably 60 to 95, more preferably 60 to 9
It is 0, more preferably 60 to 85.

Specific examples of the α, β-unsaturated carboxylic acid alkyl ester monomer (M) in the copolymer (II) of the present invention include methyl acrylate, ethyl acrylate, propyl acrylate and acryl. Butyl acid, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, dodecyl acrylate, isopropyl acrylate, isobutyl acrylate, acrylic acid-sec-butyl 2-ethylhexyl acrylate, 2-pentyl acrylate, acrylic 2-hexyl acid, 2-heptyl acrylate, 2-methylbutyl acrylate 3-methylbutyl acrylate, 3-methoxybutyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, Methacrylic acid Hexyl, heptyl methacrylate, octyl methacrylate, dodecyl methacrylate, isopropyl methacrylate, isobutyl methacrylate,-sec-butyl methacrylate, 2-ethylhexyl methacrylate, 2-pentyl, methacrylic acid 2
-Hexyl, 2-heptyl methacrylate, 2-methylbutyl methacrylate, 3-methylbutyl methacrylate, 3-methoxybutyl methacrylate, etc., and one kind or a total of two or more kinds of monomers selected from them. (M) is (M) / [(M) +
The value of (Y)] is preferably 0.75 or more and more preferably 0.85 or more in terms of weight. The remainder is composed of a monomer (Y) copolymerizable with an α, β-unsaturated carboxylic acid alkyl ester, and includes, for example, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, and chloroacrylonitrile, styrene. , Aromatic vinyl monomers such as α-methylstyrene, α-chlorostyrene and vinyltoluene, n-phenylmaleimide, n-
Examples thereof include maleimide monomers such as cyclohexylmaleimide, unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid and maleic anhydride.

Further, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane. The copolymer (II) may be crosslinked with trimethacrylate, triallyl isocyanurate, divinylbenzene or the like to control the hardness to the extent that the vibration damping property is not impaired.

When the resin composition requires high rigidity and high vibration damping property, the α, β-unsaturated carboxylic acid alkyl ester monomer (M) is preferably methyl methacrylate. The molecular weight of this copolymer (II) is G
Polystyrene-based weight average molecular weight of 5,000 by PC (gel permeation chromatography)
It is preferable that it is in the range of 00000, and
The range of 200,000 is more preferable. 500
When it is less than 0, the vibration damping property and the rigidity are poor, and 500000
If it exceeds the range, the vibration damping property is poor and it becomes difficult to obtain good molding processability.

Regarding the damping property, the loss coefficient η at the operating temperature is preferably 0.05 or more, more preferably 0.06 or more, and further preferably 0.08 or more. Further, in order to use a resin composition having excellent vibration damping properties as a structure, it is preferable that the rigidity is 10000 kgf / cm ² or more, more preferably 15000 kgf / cm ² as ASTM D790 flexural modulus.
More preferably, it is 20000 kgf / cm ² or more.

Further, in order to have easy moldability, it is preferable that the resin composition is not a multilayer composite material such as a vibration damping steel plate but a single layer material and is thermoplastic. Therefore, the blending ratio of the thermoplastic polyurethane (I) and the copolymer (II) is 0.5 to 50% by weight of the thermoplastic polyurethane (I) and 99.5 to 5 of the copolymer (II).
0% by weight is preferable, (I) is 5 to 30% by weight, (II) is more preferably 95 to 70% by weight, (I) is 10 to 30% by weight, and (II) is 90% by weight. ~ 7
It is more preferably 0% by weight. (I) + (I
I) was added so that the total amount was 100% by weight, and the average particle diameter of the thermoplastic polyurethane (I) as the dispersion layer was 0.0.
It should be in the range of 1 to 10 μm.

When the content of the thermoplastic polyurethane (I) is less than 0.5% by weight, the damping property is insufficient regardless of the average particle size of the dispersion layer, and when it exceeds 50% by weight, the rigidity is low.
It becomes difficult to use it as a structure, the fluidity is insufficient, and the moldability is insufficient. The blending method of the thermoplastic polyurethane (I) and the copolymer (II) may be selected from known kneading methods. Powder, beads, flakes,
Chips or pellets of (I) and (II) can be kneaded with a roll mill, kneader, Banbury mixer, single-screw extruder, twin-screw extruder or the like to obtain a composition. However, the average particle diameter of the dispersion layer is 0.01 to 10
In order to control in the range of μm, an apparatus capable of increasing the shear stress is preferable, and the extrusion temperature, screw pattern, screw rotation speed, etc. may be modified.

It is optional to add a known heat stabilizer, ultraviolet absorber, lubricant, release agent, flame retardant, antistatic agent, etc. to the resin composition of the present invention. However, the processing temperature when forming the resin composition of the present invention by melt-kneading, or the molding processing temperature also means to prevent thermal decomposition of the thermoplastic polyurethane (I) or the resin composition of the present invention prepared after kneading. , 240 ° C. or lower, and more preferably 220 ° C. or lower.

[0018]

The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The parts used below are parts by weight. (Production Method of Copolymer II-1) 150 Parts of Deionized Water,
1.3 parts of sodium dioctyl sulfosuccinate (trade name Lapizole) was placed in a polymerization layer with a reflux condenser, and the temperature was raised to 70 ° C. while substituting the gas phase with nitrogen. 90 parts of methyl methacrylate, 10 parts of styrene, 0.8 part of t-dodecyl mercaptan, 0.2 part of cumene hydroperoxide, 100 parts of deionized water, 0.1 part of sodium formaldehyde sulfoxynate, sulfuric acid Stirring polymerization was carried out while continuously adding an aqueous solution prepared by dissolving 0.005 parts of ferrous iron and 0.05 parts of disodium ethylenediaminetetraacetate for 7 hours. During this period, the reaction temperature was controlled at 70 ° C., and after the addition was completed, post-polymerization was performed to complete the reaction. The polymerization rate was 99%. The polymerized latex obtained is subjected to salt folding, dehydration and drying,
Flaked. (Method for producing Copolymer II-2) 150 parts of deionized water,
1.3 parts of sodium dioctyl sulfosuccinate (trade name Lapizole) was placed in a polymerization layer with a reflux condenser, and the temperature was raised to 70 ° C. while substituting the gas phase with nitrogen. Methyl methacrylate 90 parts, acrylonitrile 10 parts, t-dodecyl mercaptan 0.8 parts, cumene hydroperoxide 0.
7 parts of an aqueous solution containing 100 parts of deionized water, 0.1 part of sodium formaldehyde sulfoxynate, 0.005 part of ferrous sulfate and 0.05 part of disodium ethylenediaminetetraacetate. Stirring polymerization was carried out with continuous addition over time. During this time,
The reaction temperature was controlled at 70 ° C., and after the addition was completed, post-polymerization was performed to complete the reaction. The polymerization rate was 99%. The obtained polymerized latex was salted, dehydrated and dried to form flakes.

[0019]

Example 1 As a thermoplastic polyurethane, 25 parts of Desmopan 590 (Bayer Co., polyester system, hardness 90) and 75 parts of Delpet 80N (PMMA, Asahi Kasei Co., Ltd.) were blended, and a twin-screw extruder (PCM) was used. -30,
Kneading disk L: 2 using Ikegai Iron Works Co., Ltd.
Kneading disk R: 3 pieces, sealing: 1 piece, and kneading was carried out at 220 ° C. with a screw pattern mainly composed of shallow grooves (pattern A) to obtain pellets of the resin composition of Example 1. Using this pellet, 220 ℃
A test piece for physical property test was prepared by using an injection molding machine and evaluated.

[0020]

Example 2 Evaluations were made in the same manner as in Example 1 except that the extrusion temperature was 210 ° C.

[0021]

[Example 3] Example 1 except that a kneading disc L: 2 and a kneading disc wide were used to form a screw pattern (pattern B) mainly composed of shallow grooves.
It evaluated similarly to.

[0022]

Comparative Example 1 Example 1 was repeated except that a kneading disk and a seal ring were not used, and a screw pattern (pattern C) mainly composed of shallow grooves having a longer groove pitch than the shallow grooves used in patterns A and B was used. It evaluated similarly to.

[0023]

[Examples 4 to 14 and Comparative Examples 2 to 4] Evaluations were made in the same manner as in Example 1 under the conditions shown in Table 1. Comparative Examples 3 and 4
It was molded and evaluated in the same manner as in Example 1. The thermoplastic polyurethane used is Desmopan 590, E980.
(Polycarbonate type, hardness 80, manufactured by Nihon Miractolan Co., Ltd.), E990 (polycarbonate type, hardness 90, manufactured by Nihon Miractoran Co., Ltd.), E390 (polyether type, hardness 90, manufactured by Nihon Miractoran Co., Ltd.), E590 (polycaprolactone type, hardness 90). , Manufactured by Nihon Miractolane Co., Ltd.) and P8765 (polycarbonate type, hardness 65, manufactured by Dainichiseika Co., Ltd.), and as the copolymer, Delpet 80N and the above-mentioned copolymers II-1 and II-2 are used. I was there. (Test Method) (Average Particle Diameter of Dispersion Layer) An electron micrograph of an ultrathin section of the resin composition was taken, and the arithmetic average of the major axis and the minor axis of the dispersion layer particles was taken as the particle diameter. I calculated the average. (Flexural Modulus) Measured at 23 ° C. according to ASTM D790. (Method of measuring vibration damping performance (loss coefficient η)) A dumbbell (ASTM D638 type 1: thickness 3 mm) molded by an injection molding machine has a loss coefficient η at 23 ° C. of a 2-channel FFT (fast Fourier transform) device ( 203
2 type: manufactured by B & K Co., Ltd.) was measured by the half-width method by the cantilever method with non-contact random vibration, and the value in terms of 500 Hz was obtained.

[0024]

[Table 1]

[0025]

The resin composition of the present invention has excellent vibration damping properties,
It has the characteristics of high rigidity and easy molding. Further, the resin composition of the present invention can be used as a structure of a vacuum cleaner, a shaver or the like in a field requiring vibration damping property, for example, in a field of home electric appliances, and is industrially very useful.

[Procedure amendment]

[Submission date] August 27, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in vibration damping properties, Tsuyoshi Ko, it relates to a thermoplastic resin composition which can be easily molded.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Further, as in JP 55-153831 discloses such, is excellent in vibration damping property, in the rigidity increases the rigidity of the lower resin material, filler, for example Karasufu I error or talc (main component There is also a method of adding calcium carbonate). By this method, the rigidity of the resin is certainly improved, but new drawbacks such as low impact strength, large anisotropy of impact strength, and significant decrease in surface gloss are newly generated. Limited use. In addition, since the specific gravity increases due to the addition of the filler, it was not suitable for applications where weight reduction is required as in the case of damping steel plates.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Further, as a material having a vibration damping property, a thermoplastic elastomer, for example, a thermoplastic polyurethane can be mentioned. However, when it is used alone, its rigidity is insufficient to be used as a structure. Further, a composition of polyurethane and polymethacrylate is known in JP-A-53-148196, but the balance between vibration damping property and rigidity is not sufficient for use as a structure.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

The average particle size of the dispersion layer is 10 μm or less
As means for this, for example, shear stress during kneading,
Melt viscosity between polymers, interfacial tension between polymers,
The compatibility between the polymers can be utilized. To
The thermoplastic polyurethane (I) and the copolymer (I
I) is blended and kneaded with, for example, an extruder.
At this time, it is preferable that the shear stress be as high as possible.
Is 10³Pa or more, more preferably 10^FourPa or higher
And preferably 10⁶Pa or higher. for that purpose,
1) List the rotation speed of the extruder. 2) Extruder screen
In the clew pattern, the pattern that takes a share
You just have to select it, and in terms of screw parts, for example,
For example, seal ring, kneading disc L or Y
Do not use many screw parts with short pitches
It 3) It is possible to use means such as extrusion at a low temperature.
Wear. However, there is concern about heat deterioration of the resin due to shear heat generation.
In some cases, some restrictions may have to be
It The extrusion temperature is at least (I), or
It must be at a temperature at which (II) melts. Extruder
The shear stress when kneading with a
The same as the average particle size of the dispersion layer obtained by using a machine
Shear to obtain average particle size of dispersed layer by capillograph
It can be obtained as stress. About heat
Melt viscosity of plastic polyurethane (I) and copolymer (II)
The degree ratio is preferably in the range of 0.01 to 10,
More preferably, it is in the range of 0.05 to 5,
Consider the kneading temperature so that it is as close to 1 as possible.
Taking into consideration, select an appropriate combination of (I) and (II) and kneading temperature.
You can choose. As a means to measure melt viscosity
For example, a capillograph can be used.
For thermoplastic copolymers (I) and copolymers
The interfacial tension of the resin composition after blending with (II)
It is sufficient to lower the amount as much as possible. For example, a compatibilizer is also used.
You can As compatibilizer, polyurethane and
Block with α, β-unsaturated carboxylic acid alkyl ester
Copolymers and the like are effective, but are not limited to these.
Yes. For copolyester with thermoplastic polyurethane (I)
SP (Solubility Par) between united (II)
It is preferable that the value
ItThisThe SP value of these resins is, for example, S
The formula of mall can be used. For example, thermoplastic
Polyurethane (I)Is10.0 cal^0.5/ C
m^1.5PMMA (Polymethyi) belonging to Copolymer (II)
(Meth) resin is 9.3 cal ^0.5/ Cm^1.5
Is. For example, PMMA copolymer with acrylonitrile
Increase the SP value by 10.0cal^0.5/ Cm
^1.5You should be close to.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Specific examples of the α, β-unsaturated carboxylic acid alkyl ester monomer (M) in the copolymer (II) of the present invention include methyl acrylate, ethyl acrylate, propyl acrylate and acryl. butyl, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, dodecyl acrylate, isopropyl acrylate, isobutyl acrylate,-sec-butyl acrylate, 2-ethylhexyl acrylate,
2-pentyl acrylate, 2-hexyl acrylate, 2-heptyl acrylate, 2-methylbutyl acrylate ,
3-methylbutyl acrylate, 3-methoxybutyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, dodecyl methacrylate,
Isopropyl methacrylate, isobutyl methacrylate,
Methacrylic acid-sec-butyl methacrylate, 2-ethylhexyl methacrylate, 2-pentyl methacrylate, 2-hexyl methacrylate, 2-heptyl methacrylate, 2-methylbutyl methacrylate, 3-methylbutyl methacrylate,
3-methoxybutyl methacrylate and the like can be mentioned, and the sum (M) of one kind or two or more kinds of monomers selected from these is (M) / [(M) + from the viewpoint of vibration damping property.
The value of (Y)] is preferably 0.75 or more and more preferably 0.85 or more in terms of weight. The remainder is composed of a monomer (Y) copolymerizable with an α, β-unsaturated carboxylic acid alkyl ester, and includes, for example, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, and chloroacrylonitrile, styrene. , Aromatic vinyl monomers such as α-methylstyrene, α-chlorostyrene and vinyltoluene, n-phenylmaleimide, n-
Examples thereof include maleimide monomers such as cyclohexylmaleimide, unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid and maleic anhydride.

Claims (2)

[Claims] 1. A thermoplastic polyurethane (I), α, β
An unsaturated carboxylic acid alkyl ester monomer and optionally a copolymer (II) comprising a monomer copolymerizable therewith, wherein the thermoplastic polyurethane (I) is present as a dispersion layer, and The average particle size of the dispersion layer is 0.0
A vibration-damping resin composition, which is in the range of 1 to 10 μm. 2. The vibration-damping resin composition according to claim 1, wherein the thermoplastic polyurethane (I) is a polycarbonate type.