JPH0625281B2 - Acrylonitrile butadiene rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a modified rubber composition using a non-rubber substance obtained from serum produced as a by-product during the production of natural rubber, and particularly to physical properties of acrylonitrile-butadiene rubber without impairing its characteristics. And an acrylonitrile butadiene rubber composition having improved properties.

<Prior Art> Acrylonitrile butadiene rubber (NBR) is a random copolymer of butadiene and acrylonitrile (AN), and is an amorphous and irregular rubber. In particular, it has excellent oil resistance, heat resistance, chemical resistance, wear resistance, etc., and has been widely used for applications utilizing these characteristics.

However, there is a problem with viscoelastic properties such as impact resilience, and there is a problem when used as a packing material.

In addition, the green strength was low, and there were problems with the shape retention and workability of the green.

On the other hand, in the natural rubber manufacturing process, the remaining liquid after removing the solidified rubber is an aqueous solution called Serum,
In many cases, it is discarded as it is, and there is a problem of environmental pollution due to the decay of non-rubber components such as proteins and sugars contained therein. There is also a method of treating serum in a purification treatment tank, but it is not effective because it has a bad rotten odor and is a pollution problem, although it costs a lot of money.

If this serum can be used as an industrially useful substance, the efficiency of the rubber industry will be increased and it will be effective in resource saving.

<Objects of the Invention> An object of the present invention is to improve the mechanical strength and the compression fatigue resistance of the acrylonitrile butadiene rubber without impairing the characteristics of the acrylonitrile butadiene rubber by effectively using the natural rubber latex serum industrially.

<Structure of the Invention> The present invention is characterized in that the acrylonitrile-butadiene rubber is blended with 0.5 to 10 pHR or more of a powdery non-rubber component obtained from the remaining serum obtained by coagulating and removing the rubber component of natural rubber latex. A butadiene rubber composition is provided.

The present invention will be described in more detail below.

The powdery non-rubber component obtained from the natural rubber latex serum used in the present invention is a substantially spherical powder, and preferably has an average particle size of 10 to 100 μm. The component composition varies depending on the component of the natural rubber latex as the raw material and cannot be strictly limited, but about 50% of crude protein such as α-globulin and hevein, about 30% of sugar, K, Mg,
About 15 ash (inorganic components) of Cu, Fe, Na, Ca, P, etc.
%, Lipid about 2%, water about 3%, fiber 0% and other trace components, and the crude protein content is at a considerably high level.

The method for producing a powdery non-rubber component obtained from natural rubber latex serum is a coagulant from the raw material natural rubber latex, formic acid, acetic acid, sulfuric acid, etc. are used to coagulate and remove the rubber component, and the remaining serum (Serum) To use.

The composition of the natural rubber latex is shown in Table A, for example.

This natural rubber latex obtained by coagulating rubber hydrocarbons and removing it is called a serum, and in general, the serum generally contains a very small amount of rubber.

The components of the serum differ depending on the components of the natural rubber latex, and various materials can be used as raw materials, but the serum contains about 0.5 wt% of rubber and about 2 to 5 wt% of non-rubber.
This may be used after removing the rubber content by centrifugation or the like.

A non-rubber (solid content) concentration of 2 to 80 wt% can be used, but in view of production efficiency, manufacturing cost and process control, a serum having a solid content of 15 to 70 wt% can be used as a raw material. preferable. Normally, the solid content of the serum obtained in the natural rubber manufacturing process is about 2 to 5 wt%, so a pretreatment for concentrating the solid content to about 25 to 70 wt% by a method such as an evaporator, a centrifugal separator, or a filtration is performed. Good to do.

The above-mentioned serum is supplied in the form of microdroplets into a spray-dry container in a high temperature atmosphere of 150 to 250 ° C., and water is instantly evaporated to obtain a powder form. For this reason, the closed system spray dry method is used. The closed system spray-dry method is a method of atomizing a liquid sample and bringing the atomized droplets into contact with hot air and instantaneous droplets to evaporate the moisture and dry it into powder. There are a nozzle type that atomizes with a nozzle and a disk type that atomizes with a high-speed rotating disk. Either may be used, but the disk type is preferable because it is efficient. Disk rotation speed is 10,000 to 30,000
The rpm and nozzle pressure should be 0.5 to 2.0 kg / cm ² . If the rotation speed or pressure is outside this range, the size of the powder obtained will be 10
If the powder is out of the range of 100 μm and less than 10 μm, it tends to absorb moisture and re-solidify, or adhere to the inner wall of the spray dryer or agglomerate to deteriorate the recovery rate.
The powder obtained becomes dango-like and is not atomized. 1
If it exceeds 00μ, it is difficult to dissolve the non-rubber component in water or a solvent when it is industrially used, and the bulkiness becomes large, which is inconvenient for transportation.

Keep the drying temperature in the spray-drying container at 150-250 ° C, especially the sample inlet drying temperature at 150-250 ° C.
The sample outlet temperature is preferably 50 to 130 ° C.

If the sample drying temperature is higher than this temperature range, the resulting non-rubber component is deteriorated by heat. The non-rubber components are proteins, sugars, resins, etc., and are easily affected by heat. Since the actual sample temperature is about 100 ° C. lower than the inlet temperature, the drying temperature cannot be too high from that point as well. On the other hand, if the temperature is lower than this temperature range, the particles cannot be dried sufficiently, and do not become powdery but aggregate to become dango-like.

The acrylonitrile butadiene rubber used in the present invention may be any one, but especially acrylonitrile component 18
It is better to use the one of about 43%.

The addition ratio of the powdery non-rubber component obtained from the residual serum obtained by coagulating and removing the rubber component of the natural rubber latex to the acrylonitrile-butadiene rubber is 0.5 to 10 pHR (per hu
ndred rubber: parts by weight based on 100 parts by weight of rubber). If it is less than 0.5 pHR, the effect of the present invention cannot be obtained.
This is because if it exceeds pHR, the physical properties such as tensile strength deteriorate.

Generally, when a powdered non-rubber component obtained from the remaining serum after coagulation removal of the rubber component of natural rubber is added to a general-purpose polymer (NR, IR, SBR, etc.), if the addition amount increases at 2 pHR, Ts, El, Physical properties deteriorate, such as a decrease in mod, increase in heat generation, and deterioration in wear resistance.

However, when a powdery non-rubber component obtained from the remaining serum obtained by solidifying and removing the rubber component of natural rubber is added to acrylonitrile butadiene rubber, the characteristics of acrylonitrile butadiene rubber such as oil resistance, heat resistance, chemical resistance, and abrasion resistance The repulsion resilience of the vulcanized rubber increases, the compression set decreases, and the tan δ (loss tangent) also decreases without impairing

Further, the green strength of the NBR compound becomes high.

<Examples> Examples will be described in more detail below.

(Examples and Comparative Examples) The components having the compositions shown in Table 1 were kneaded with a Banbury mixer to form a plate material having a size of 150 × 150 × 2 mm, and 148 ° C. × 3.
Vulcanization was carried out under the condition of 0'to obtain test pieces having the numbers shown in Table 1.

Notes shown in Table 1 NRSP: Powdered non-rubber component obtained from the remaining serum after coagulation removal of the rubber component of natural rubber latex, manufacturing method, etc. are as shown in Table 2.

There was no change in the properties of the composition due to the difference in the powdered non-rubber component.

Accelerator DM: Noxceller M manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. Using the test pieces shown in Table 1, the following tests were conducted.

The results are shown in Table 3.

Rubber test method Unvulcanized rubber test (1) Mooney viscosity test; MV JIS K 6300 ML _{1 + 4} @ 100 ℃ (2) Rheometer test Rheo.Max.T. @ 160 ℃ (maximum torque) using Toyo Seiki Rheometer Rheo.Min.T. @ 160 ℃ (Minimum torque) T ₅ T ₉₅ (3) Green strength JIS No. 1 Dumbell punching with autograph 500mm /
Tensile at min, measured for M ₃₀₀ Vulcanized rubber test (1) Tensile test Tensile strength (Ts) JIS K 6301 160 ℃ × 10 'Elongation (El) JIS K 6301 Tensile stress (M) JIS K 6301 M ₁₀₀ : 100 % Modulus M ₃₀₀ : 300% modulus (2) Hardness (Hs JISA) JIS K 6301 (3) Aging test (Aging) JIS K 6301 100 ℃ × 48H Ts, El, M ₁₀₀ , Hs after aging are measured (4 ) Repulsion elasticity (Lupke) JIS K 6301 (5) Heat generation test Dynamic internal heat generation (heat build up; HBU) Dynamic permanent set (ps) Goodrich flexometer Rotation speed 1800 rpm, Stroke 4.44 mm, Load 25 kg (6) Compression set (C-set) JIS K 6301 70 ℃ × 22H (7) Loss tangent (tan δ) Viscoelasticity spectrometer Extension type strain 10 ± 2%, 20Hz, 20 ℃ (8) Complex elastic modulus (E ^* ) Viscoelasticity spectrometer Extension type strain 10 ± 2%, 20Hz, 20 ° C (9) Flex test JIS K 6301 Measurement of crack length at 30,000 and 100,000 flex cycles with 40 mm stroke.

Evaluation A: Almost no cracks C: Cracks that can be visually determined Z: Cracks occur at both ends K: Cracks occur at both ends (cut) (10) Static ozone deterioration JIS K 6301, 50pphm, 40 ° C, 20%, The degree of crack generation after 72H is shown by Cn.

From the results shown in Table 3, the acrylonitrile butadiene rubber composition of the present invention has the following characteristics.

Mechanical Properties of Acrylonitrile Butadiene Rubber (Ts, E
l, M ₁₀₀ , M ₃₀₀ , Hs), mechanical properties of aging resistance (Aging Ts, El,
M ₁₀₀ , Hs) and heat resistance are not impaired by the addition of additives.

Unvulcanized rubber has high strength (GS) and high impact resilience (Lupke).

Low compression set (C-set) and tan δ.

<Effects of the Invention> The present invention is a composition comprising acrylonitrile butadiene rubber, 0.5 to 10 pHR of a powdered non-rubber component obtained from the remaining serum obtained by removing the rubber component of natural rubber latex, and the following effects. There is.

1. Acrylonitrile butadiene rubber NBR compound has high green strength.

2. The impact resilience is increased and the dynamic viscoelasticity is improved.

3. Compression set and tan δ decrease.

Claims (1)

[Claims] 1. An acrylonitrile-butadiene rubber composition comprising acrylonitrile-butadiene rubber and 0.5 to 10 pHR of a powdery non-rubber component obtained from the remaining serum obtained by coagulating and removing the rubber component of natural rubber latex.