KR102269536B1 - Rubber composition having fire retardant and sound absorbing, and mat for reducing the floor noise comprising the same - Google Patents

Abstract

The present invention relates to a rubber composition that satisfies both flame retardancy and sound absorption at the highest grade level, and a flame retardant interlayer noise prevention mat comprising the same. The rubber composition according to the present invention comprises inexpensive butyl rubber as a rubber base, aluminum hydroxide and chlorinated paraffin as a flame retardant. , and as a foaming agent, ADCA (Azodicarbonamide) is blended in a specific content ratio, thereby satisfying both flame retardancy and sound absorption at the highest level.

Description

Flame retardant and sound-absorbing rubber composition and interlayer noise prevention mat comprising the same {Rubber composition having fire retardant and sound absorbing, and mat for reducing the floor noise comprising the same}

The present invention relates to a rubber composition that satisfies both flame retardancy and sound absorption at the highest grade level, and a flame retardant interlayer noise prevention mat comprising the same.

In multi-story buildings such as apartments and villas, which are modern residential types, shock sounds and vibrations generated during the lives of upper floors are transmitted to the lower floors, which can cause disputes between upper and lower floors. For this reason, in families with infants and children, by laying a mat of a predetermined size in the living room, etc., the impact sound and vibration transmitted to the lower floor when the child runs or plays are prevented to some extent, and the child is not injured when he falls. have.

Most of these conventional mats are composed of a single layer of foamed synthetic resin, or are formed by laminating a bottom layer (rubber base) on the lower surface of the foamed resin layer, and the bottom layer (rubber base) is butyl rubber (IIR, Isobutene-isoprene Rubber). is mainly used, but the effect of blocking shock sounds and vibrations does not meet expectations, so the possibility of disputes between the upper and lower floors exists.

Butyl rubber (or Isobutene-isoprene Rubber, IIR) is a copolymer containing mostly isobutene and a small amount of isoprene. Unlike NR, SBR, BR, and NBR, butyl rubber is a highly saturated rubber with only a small amount of double bonds. The small amount of unsaturation (double bond) provides a site necessary for vulcanization.

In addition, most of the interlayer noise prevention mats using butyl rubber on the market as a rubber base do not satisfy flame retardancy standards, so there is a problem of being vulnerable to fire.

Accordingly, the present inventors found that a rubber composition containing inexpensive butyl rubber as a rubber base, aluminum hydroxide and chlorinated paraffin as a flame retardant, and ADCA (Azodicarbonamide) as a foaming agent in a specific content ratio satisfies both flame retardancy and sound absorption at the highest level, The present invention was completed.

Registered Patent No. 10-1765870

It is an object of the present invention to provide a flame retardant and sound-absorbing rubber composition.

Another object of the present invention is to provide a flame-retardant sound-absorbing mat comprising the rubber composition.

Another object of the present invention is to provide a flame-retardant interlayer noise prevention mat comprising the rubber composition.

Another object of the present invention is to provide a flame-retardant anti-vibration material comprising the rubber composition.

Another object of the present invention is to provide a flame-retardant sound-absorbing mat comprising a rubber base made of the rubber composition.

Another object of the present invention is to provide a flame-retardant interlayer noise prevention mat comprising a rubber base made of the rubber composition.

In order to achieve the above object,

The present invention is based on 80 parts by weight of butyl rubber or halogenated butyl rubber as a rubber base; 17-23 parts by weight of aluminum hydroxide as a flame retardant; 8-12 parts by weight of chlorinated paraffin as a flame retardant; and 0.15-0.35 parts by weight of ADCA (Azodicarbonamide) as a blowing agent; It provides a flame retardant and sound-absorbing rubber composition comprising a.

In addition, the present invention provides a flame-retardant sound-absorbing mat comprising the rubber composition.

Furthermore, the present invention provides a flame-retardant interlayer noise prevention mat comprising the rubber composition.

In addition, the present invention provides a flame-retardant anti-vibration material comprising the rubber composition.

Further, the present invention is a soft EVA (Ethylene Vinyl Acetate) foamed rubber layer; PU (polyurethane) foam rubber layer; Hard EVA (Ethylene Vinyl Acetate) foamed rubber layer; PU (polyurethane) foam rubber layer; And a rubber base made of the rubber composition according to the present invention; provides a flame-retardant sound-absorbing mat, characterized in that sequentially laminated.

In addition, the present invention is a soft EVA (Ethylene Vinyl Acetate) foamed rubber layer; PU (polyurethane) foam rubber layer; Hard EVA (Ethylene Vinyl Acetate) foamed rubber layer; PU (polyurethane) foam rubber layer; And a rubber base made of the rubber composition according to the present invention; provides a flame-retardant interlayer noise prevention mat, characterized in that sequentially laminated.

The rubber composition according to the present invention contains inexpensive butyl rubber (or halogenated butyl rubber) as a rubber base, aluminum hydroxide and chlorinated paraffin as a flame retardant, and ADCA (Azodicarbonamide) as a foaming agent in a specific content ratio. has a satisfactory effect.

1 is a cross-sectional view of the flame-retardant interlayer noise prevention mat prepared in Example 2.

Hereinafter, the present invention will be described in detail.

flame retardant and sound absorption rubber composition

The present invention is based on 80 parts by weight of butyl rubber or halogenated butyl rubber as a rubber base;

17-23 parts by weight of aluminum hydroxide as a flame retardant;

8-12 parts by weight of chlorinated paraffin as a flame retardant; and

0.15-0.35 parts by weight of ADCA (Azodicarbonamide) as a blowing agent;

It provides a flame retardant and sound-absorbing rubber composition comprising a.

The flame-retardant and sound-absorbing rubber composition according to the present invention is EPDM (Ethylene Propylene Diene Monomer), natural rubber, inorganic filler, process oil, zinc oxide, stearic acid, surfactant, light blocking agent, processing aid, antioxidant, antioxidant, vulcanizing agent and At least one additive selected from the group consisting of vulcanization accelerators may be further included.

In the rubber composition according to the present invention, based on 80 parts by weight of butyl rubber or halogenated butyl rubber,

When the amount of aluminum hydroxide is less than 17 parts by weight or more than 23 parts by weight, there is a problem in that flame retardancy and sound absorption are lowered,

When the amount of paraffin chloride is less than 8 parts by weight or more than 12 parts by weight, there is a problem in that flame retardancy and sound absorption are lowered,

When the amount of ADCA (Azodicarbonamide) as a foaming agent is less than 0.15 parts by weight, there is a problem that the sound quality is lowered, and when it is more than 0.35 parts by weight, there is a problem that the flame retardancy is reduced.

Preferably,

Based on 80 parts by weight of butyl rubber or halogenated butyl rubber as the rubber base;

18.5-21.5 parts by weight of aluminum hydroxide as a flame retardant;

9-11 parts by weight of chlorinated paraffin as a flame retardant; and

0.2-0.3 parts by weight of ADCA (Azodicarbonamide) as a blowing agent;

may include.

More preferably,

Based on 80 parts by weight of butyl rubber or halogenated butyl rubber as the rubber base;

18.5-21.5 parts by weight of aluminum hydroxide as a flame retardant;

9-11 parts by weight of chlorinated paraffin as a flame retardant;

0.2-0.3 parts by weight of ADCA (Azodicarbonamide) as a blowing agent;

EPDM (Ethylene Propylene Diene Monomer) 14.5-15.5 parts by weight;

4.5-5.5 parts by weight of natural rubber;

43-47 parts by weight of silica as an inorganic filler;

0.15-0.25 parts by weight of carbon as an inorganic filler;

28-32 parts by weight of calcium carbonate as an inorganic filler;

10-14 parts by weight of process oil;

6-8 parts by weight of zinc oxide;

1-2 parts by weight of stearic acid;

PEG-4000 1-2 parts by weight;

9-11 parts by weight of titanium dioxide;

1-2 parts by weight of processing aid;

1-2 parts by weight of an antioxidant;

1.5-2.5 parts by weight of antioxidant;

1.0-1.4 parts by weight of a vulcanizing agent; and

5-6 parts by weight of a vulcanization accelerator (anti-bruising agent); may be included.

In the rubber composition according to the present invention,

The 'butyl rubber' serves as a rubber base and sound absorbing material,

The 'flame retardant' serves to impart flame retardancy,

The 'foaming agent' serves to reduce the weight of the rubber base and assist in sound absorption.

In the present invention, the 'flame retardant' not only affects the flame retardancy, but also affects the sound absorption according to the content, and the 'foaming agent' generates bubbles in the rubber base to reduce the weight. There is a technical feature in the point that it also affects the flame retardancy.

mat and anti-vibration material

The present invention provides a flame-retardant sound-absorbing mat, a flame-retardant interlayer noise prevention mat, a flame-retardant anti-vibration material, and the like, comprising the flame-retardant and sound-absorbing rubber composition.

In addition, the present invention is a soft EVA (Ethylene Vinyl Acetate) foamed rubber layer;

PU (polyurethane) foam rubber layer;

Hard EVA (Ethylene Vinyl Acetate) foamed rubber layer;

PU (polyurethane) foam rubber layer; and

It provides a flame-retardant sound-absorbing mat, or a flame-retardant interlayer noise prevention mat, characterized in that the rubber base made of the rubber composition according to the present invention is sequentially laminated.

In the mat according to the present invention, the specific gravity of the soft EVA foamed rubber layer may be 0.65-0.75, and the specific gravity of the rigid EVA foamed rubber layer may be 1.1-1.2. Specifically, since the soft EVA foamed rubber layer is laminated on the top layer of the mat, soft properties are required, and the hard EVA foamed rubber layer is inserted in the middle of the mat, so it needs hard properties to maintain the mat shape.

In the mat according to the present invention, the specific gravity of the PU foamed rubber layer may be 0.2-0.3. Specifically, the PU foamed rubber layer serves to absorb the impact.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited by the following examples.

< Example 1> Flame retardant and sound absorption Manufacture of 'rubber base' for testing

With the composition of Table 1 below,

Put butyl rubber, EPDM, and natural rubber in a kneader device and pass through the USSR step for 15-20 minutes at a temperature within the range of 70-90 ° C. Then, inorganic fillers, flame retardants and additives ( ingredients) and kneading was carried out within the range of about 130-200 seconds.

Next, a vulcanizing agent, accelerator (anti-bruising agent), and ADCA (Azodicarbonamide) foaming agent are added in an 18-inch roller device, and lowered for about 15 minutes at a roller temperature of 60-70°C. After working, thickness 10mm*width 300mm* It was made in the form of a sheet with a length of 1000 mm. The prepared sheet was aged for 6-10 hours in a rubber aging room at 18-20 ° C, cut to a size suitable for the purpose, and molded and pressed into a shape suitable for the purpose.

The sample for the flame retardancy test was cut to 130×13×2 mm size

The sample for the sound absorption test was cut to a size of 250 × 250 × 10 mm.

Ingredient name content
(parts by weight) function or role One butyl rubber 80 Rubber base and sound absorption role 2 EPDM
(Ethylene Propylene Diene Monomer) 15 The role of complementing the physical properties of butyl rubber 3 natural rubber 5 Non-slip rubber base 4 silica 45 Inorganic filler (the role of excipient) 5 Carbon (Graphite) 0.2 Inorganic filler (the role of excipient) 6 process oil
(CAS no. 64742-65-0; Manufacturer: Gain Co., Ltd.; Product name: P-4) 12 solvent role 7 calcium carbonate 30 Inorganic filler (the role of excipient) 8 zinc oxide 7 crosslinking aid 9 stearic acid 1.5 crosslinking aid 10 PEG-4000
(CAS no. 25322-68-3; Manufacturer: ICI Surfactants, UK) 1.5 Surfactant (Auxiliary role of mixing inorganic fillers and rubber components) 11 Titanium dioxide (TiO ₂ ) 10 Preserve rubber base color 12 processing aid
(Manufacturer: STRUKTOL, Germany; Product name: FL) 1.5 Helps in mixing rubber components 13 paraffin wax
(Manufacturer: Daewoon Co., Ltd.; Product name: SUNOC#150) 1.5 Anti-aging agent (light blocking role) 14 Butylated Hydroxy Toluene (BHT) 2 Antioxidants (to prevent mold) 15 ADCA (Azodicarbonamide) 0.25 Foaming agent (reducing weight and complementing sound absorption) 16 aluminum hydroxide 20 flame retardant 17 Chlorinated paraffin 10 flame retardant 18 sulfur 1.2 Vulcanizing agent (crosslinking rubber component) 19 N-Cyclohexyl-2-benzothiazolylsulfenamide (CAS no.: 95-33-0) One Vulcanization accelerator (acting to prevent bruising from bleeding out of the finished product) 20 2,2'-Dithiobis(benzothiazole) (CAS no.: 120-78-5) 1.5 Vulcanization accelerator (acting to prevent bruising from bleeding out of the finished product) 21 Bis(dimethylthiocarbamoyl) disulfide (CAS no.: 137-26-8) 1.5 Vulcanization accelerator (acting to prevent bruising from bleeding out of the finished product) 22 Zinc(II) Dibutyldithiocarbamate (CAS no.: 136-23-2) 1.5 Vulcanization accelerator (acting to prevent bruising from bleeding out of the finished product)

The samples prepared in Examples 1-1 to 3-5 of Table 3 below are,

'Butyl rubber' as a rubber base,

'Aluminum hydroxide' as the first flame retardant,

'Chlorinated paraffin' as a second flame retardant,

The content of the remaining additives except for 'ADCA (Azodicarbonamide)' as a foaming agent was used in the same manner as described in Table 1 above.

< Example 2> Manufacture of flame retardant interlayer noise prevention mat

Soft EVA (Ethylene Vinyl Acetate) foam layer <specific gravity 0.7>;

PU (polyurethane) foamed rubber layer <specific gravity 0.25>;

Hard EVA (Ethylene Vinyl Acetate) foam layer <specific gravity 1.15>;

PU (polyurethane) foamed rubber layer <specific gravity 0.25>; and

A rubber base prepared from the rubber composition of Example 1 was sequentially laminated, and a mat was prepared through an adhesion process.

Here, the thickness of each layer is 5 mm except for the rubber base 10 mm.

1 is a cross-sectional view of the flame-retardant interlayer noise prevention mat prepared in Example 2.

< Experimental example 1> Flame retardant and sound absorption evaluation

Flame retardant evaluation method

For the flame retardancy evaluation, the 'UL 94 V (Vertical Burning Test)' evaluation method used by the Korea Institute of Construction and Living Environment Test using the 125 × 13 × 10 mm size rubber base prepared in Example 1 as a flame retardant test sample was used. and the results are shown in Table 3 below.

Specifically, the UL 94 V flame retardancy evaluation is to evaluate the combustion aspect of the product and the degree of flame propagation to the surroundings when a flame is applied in the vertical direction of the plastic product, and the specimen is carried out with a size of 130 × 13 × 2 mm, 20 After contacting the specimen with a flame of mm length for 10 seconds, measure the combustion time t1 of the specimen and record the combustion pattern. When the combustion is finished after the first contact, the combustion time t2 and the glowing time t3 of the specimen after contacting for 10 seconds are measured, and the combustion pattern is recorded. Finally, by determining the combustion time and combustion pattern of t1, t2, and t3 (whether or not the cotton wool ignites by dripping, whether it burns up to the clamp, etc.), the grade is set to V-0 (highest grade), V-1, V-2. calculated by grade.

As shown in Table 2 below, the evaluation criteria are graded according to the combustion time t1, t2, t3 and the combustion pattern of the specimen.

Assessment Methods V-0 V-1 V-2 Individual burn time (t1 or t2) ≤10 seconds ≤30 seconds ≤30 seconds Total combustion time by pretreatment condition (t1+t2) ≤50 seconds ≤250 seconds ≤250 seconds Combustion and spark formation time after secondary contact (t2+t3) ≤30 seconds ≤60 seconds ≤60 seconds Burning up to the clamp (125mm mark) No No No Ignition of cotton wool by spark drop No No Yes

sound absorption (Shock Sound Reduction) Evaluation Method

Sound absorption evaluation is 'KS F2865:2015 (laboratory measurement method for light weight and weight impact sound reduction of floor surface finishing materials), which is used by the Korea Construction Living Environment Testing Institute using the flame-retardant interlayer noise prevention mat prepared in Example 2 as a sound absorption test sample. The amount of floor impact sound level reduction was measured by the test method of ', and the results are shown in Table 3 below.

Specifically, the volume of the collection room is 57.02m ² , and the reinforced concrete structure sample [slab thickness 210mm; wall thickness 250mm; Shape: Rectangular hexahedron (ISO 10140-5 Type)] before and after installing the flame-retardant interlayer noise prevention mat prepared in Example 2, various impacts (100, 125, 160, 200, 250, 315, 400, 500 , 630, 800, 1000, 1250, 1600, 2000, 2500, 3150 Hz) and the average reduction (dB) and average reduction rate (%) of the transmitted impact sound were measured and the results are shown in Table 3 below.

For reference, products with an average impact sound reduction rate exceeding 60% are “Class S” for sound absorption (sound insulation), “Class A” for products with 55-60%, and “B” for products with less than 55%. class".

Ingredients Included (parts by weight) Flame-retardant grade shock sound butyl rubber flame retardant blowing agent aluminum hydroxide Chlorinated paraffin ADCA (Azodicarbonamide) average decrease average rate of decline Example
1-1 80 17 10 0.25 V-1 35.8dB Class A
57.1% Example
1-2 80 18.5 10 0.25 V-0 37.8dB S class
60.2% Example
1-3 80 20 10 0.25 V-0 38.4dB S class
61.2% Example
1-4 80 21.5 10 0.25 V-0 38.2dB S class
60.9% Example
1-5 80 23 10 0.25 V-1 34.9dB Class A
55.6% Example
2-1 80 20 8 0.25 V-1 35.9 dB Class A
57.2% Example
2-2 80 20 9 0.25 V-0 38.0dB S class
60.6% Example
2-3 80 20 10 0.25 V-0 38.4dB S class
61.2% Example
2-4 80 20 11 0.25 V-0 37.9dB S class
60.4% Example
2-5 80 20 12 0.25 V-1 35.0dB Class A
55.8% Example
3-1 80 20 10 0.15 V-0 34.1dB Class B
54.3% Example
3-2 80 20 10 0.20 V-0 37.9dB S class
60.4% Example
3-3 80 20 10 0.25 V-0 38.4dB S class
61.2% Example
3-4 80 20 10 0.30 V-0 38.5dB S class
61.4% Example
3-5 80 20 10 0.35 V-2 38.9 dB S class
62.0%

As shown in Table 3, the contents of 1) butyl rubber, 2) flame retardants (aluminum hydroxide and chlorinated paraffin), and 3) blowing agent were confirmed to be important factors for flame retardancy and sound absorption of the rubber base sample, Example 1-1 In Examples 3-5, the samples satisfying both the flame retardancy 'V-0 grade' and the average impact sound reduction rate 'S grade' appeared only at a specific content ratio, indicating that there is a critical significance.

< Experimental example 2> Human Hazard Assessment

In order to find out the harmfulness of the rubber base prepared in Example 1 to the human body, an experiment was conducted as follows. Specifically, a human hazard evaluation was requested from the Korea Institute of Construction and Living Environment, and the results are shown in Table 4 below.

Test Items unit Test Methods Test result Polybrominated Biphenyls (PBBs) - - - One Bromobiphenyl mg/kg (One) non-detection 2 Dibromobiphenyl non-detection 3 Tribromobiphenyl non-detection 4 Tetrabromobiphenyl non-detection 5 Pentabromobiphenyl non-detection 6 Hexabromobiphenyl non-detection 7 Heptabromobiphenyl non-detection 8 Octabromobiphenyl non-detection 9 Nonabromobiphenyl non-detection 10 Decabromobiphenyl non-detection Polybrominated Diphenyl Ethers (PBDEs) - - - 11 Bromodiphenyl ether mg/kg (One) non-detection 12 Dibromodiphenyl ether non-detection 13 Tribromodiphenyl ether non-detection 14 Trtrabromodiphenyl ether non-detection 15 Pentabromodiphenyl ether non-detection 16 Hexabromodiphenyl ether non-detection 17 Heptabromodiphenyl ether non-detection 18 Octabromodiphenyl ether non-detection 19 Nonabromodiphenyl ether non-detection 20 Decabromodiphenyl ether non-detection 21 Lead (Pb) (2) non-detection 22 Cadmium (Cd) (2) non-detection 23 Mercury (Hg) (3) non-detection 24 Hexavalent Chromium (Cr ^{6 +} ) (4) non-detection (1) IEC 62321-6:2015
(2) IEC 62321-5:2013
(3) IEC 62321-4:2013
(4) IEC 62321-7-2:2017

As shown in Table 4, it was found that the rubber base prepared in Example 1 was safe because no substances harmful to the human body were detected.

So far, with respect to the present invention, the preferred embodiments have been looked at. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated not in the foregoing description, but in particular in the claims, and all differences within the scope equivalent thereto should be construed as included in the present invention.

Claims (13)

Based on 80 parts by weight of butyl rubber as a rubber base;
18.5-21.5 parts by weight of aluminum hydroxide as a flame retardant;
9-11 parts by weight of chlorinated paraffin as a flame retardant; and
0.2-0.3 parts by weight of ADCA (Azodicarbonamide) as a blowing agent;
A flame retardant and sound-absorbing rubber composition comprising a.
delete According to claim 1,
The composition is selected from the group consisting of EPDM (Ethylene Propylene Diene Monomer), natural rubber, inorganic filler, process oil, zinc oxide, stearic acid, surfactant, light blocking agent, processing aid, antioxidant, antioxidant, vulcanizing agent and vulcanization accelerator A rubber composition, characterized in that it further comprises one or more additives.
According to claim 1,
Based on 80 parts by weight of butyl rubber as the rubber base;
18.5-21.5 parts by weight of aluminum hydroxide as a flame retardant;
9-11 parts by weight of chlorinated paraffin as a flame retardant;
0.2-0.3 parts by weight of ADCA (Azodicarbonamide) as a blowing agent;
EPDM (Ethylene Propylene Diene Monomer) 14.5-15.5 parts by weight;
4.5-5.5 parts by weight of natural rubber;
43-47 parts by weight of silica as an inorganic filler;
0.15-0.25 parts by weight of carbon as an inorganic filler;
28-32 parts by weight of calcium carbonate as an inorganic filler;
10-14 parts by weight of process oil;
6-8 parts by weight of zinc oxide;
1-2 parts by weight of stearic acid;
PEG-4000 1-2 parts by weight;
9-11 parts by weight of titanium dioxide;
1-2 parts by weight of processing aid;
1-2 parts by weight of an antioxidant;
1.5-2.5 parts by weight of antioxidant;
1.0-1.4 parts by weight of a vulcanizing agent; and
5-6 parts by weight of a vulcanization accelerator; a rubber composition comprising a.
A flame-retardant sound-absorbing mat comprising the rubber composition of claim 1.
A flame-retardant interlayer noise prevention mat comprising the rubber composition of claim 1.
A flame retardant anti-vibration material comprising the rubber composition of claim 1 .
Soft EVA (Ethylene Vinyl Acetate) foamed rubber layer;
PU (polyurethane) foam rubber layer;
Hard EVA (Ethylene Vinyl Acetate) foamed rubber layer;
PU (polyurethane) foam rubber layer; and
The rubber base made of the rubber composition of claim 1; flame-retardant sound-absorbing mat, characterized in that sequentially laminated.
9. The method of claim 8,
The specific gravity of the soft EVA foamed rubber layer is 0.65-0.75,
The specific gravity of the hard EVA foamed rubber layer is a flame-retardant sound-absorbing mat, characterized in that 1.1-1.2.
9. The method of claim 8,
The specific gravity of the PU foamed rubber layer is a flame-retardant sound-absorbing mat, characterized in that 0.2-0.3.
Soft EVA (Ethylene Vinyl Acetate) foamed rubber layer;
PU (polyurethane) foam rubber layer;
Hard EVA (Ethylene Vinyl Acetate) foamed rubber layer;
PU (polyurethane) foam rubber layer; and
A flame-retardant interlayer noise prevention mat characterized in that the rubber base made of the rubber composition of claim 1 is sequentially laminated.
12. The method of claim 11,
The specific gravity of the soft EVA foamed rubber layer is 0.65-0.75,
The flame retardant interlayer noise prevention mat, characterized in that the specific gravity of the hard EVA foamed rubber layer is 1.1-1.2.
12. The method of claim 11,
The fire retardant interlayer noise prevention mat, characterized in that the specific gravity of the PU foamed rubber layer is 0.2-0.3.

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