JP2734666B2 - Asphalt composition - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an asphalt composition for road pavement, and particularly to a fluid-resistant asphalt composition such as heavy traffic road pavement.
An object of the present invention is to provide a rubber-containing asphalt composition suitable for a field requiring strict requirements such as abrasion resistance and crack resistance.

(Prior art) A composition comprising an asphalt and an aggregate is relatively stable, has excellent wear characteristics, does not require a long curing period at the time of construction, and is characterized by being inexpensive. Widely used as pavement materials for roads and the like.

However, since the viscosity of asphalt is highly temperature-dependent, it tends to soften and rut in the summer, and harden in the winter to crack and harden due to heavy traffic caused by traffic such as chains. There is.

(Problems to be Solved by the Invention) In order to improve this, a pavement mixture using a modified asphalt containing a polymer material such as rubber or resin as a binder is used. In a traffic pavement or the like, a sufficient reforming effect is not always obtained, and problems such as rubbing, flow, and wavy deformation in a short period of time, and abrasion, cracking, and peeling occur. Therefore, further improvement is strongly desired, for example, introduction of a polar group into styrene-butadiene rubber (hereinafter abbreviated as SBR) (Japanese Patent Publication No.
Addition of carboxy-modified polyolefin (JP-A-60-158256), enlargement of particle size of SBR (JP-A-60-252644), high Mooney SBR and low Mooney SBR
(JP-A-61-95101) and the like.

In view of such circumstances, the present inventors have conducted intensive studies to develop a novel rubber-containing asphalt composition for road pavement, and as a result, have reached the present invention.

(Means for Solving the Problems) The present invention provides an asphalt composition excellent in both asphalt physical properties such as rutting resistance, flow resistance, crack resistance, and peeling resistance and workability (workability). This object is achieved by blending asphalt with SBR having a very broad molecular weight distribution using a specific molecular weight regulator.

That is, the present invention contains at least 30% by weight or more of SBR obtained by emulsion polymerization of 0.05 to 5.0 parts by weight of n-octyl mercaptan as a necessary component among the molecular weight regulators, and has a molecular weight of 4.5 × 10 ⁴ or less as a low molecular weight component. 15% by weight or more, and 30% by weight or more of a high molecular weight component having a molecular weight of 5.0 × 10 ⁵ or more.
35% by weight, Mooney viscosity (ML1 _{+ 4} , 100 ℃), 50-140
The purpose of the present invention is to provide a modified asphalt obtained by mixing 1 to 10 parts by weight of SBR in the range of 1 to 100 parts by weight of asphalt and an asphalt pavement composition obtained by mixing an aggregate with the modified asphalt.

In the present invention, the molecular weight and molecular weight distribution of SBR can be determined under the following conditions.

"GPC (HLC-802R)" column manufactured by Toyo Soda Co., Ltd .; "Staigell" manufactured by WATERS 10 ⁶ +10 ⁵ +10 ⁴ +10 ³ mobile phase; tetrahydrofuran (THF) pretreatment; after dissolving the sample in THF, Millipore The sample solution is passed through a 1 μm filter manufactured by Toshiba Corporation and the solution is measured.

 Hereinafter, the present invention will be described in detail.

The asphalt used in the present invention may be a commonly used one, such as straight asphalt for pavement, lake asphalt, blown asphalt, semi-blown asphalt and the like.

The SBR used in the present invention can be obtained by one-stage polymerization by an emulsion polymerization method using a specific molecular weight regulator. As a method of obtaining SBR having a certain amount of low molecular weight component and high molecular weight component and a wide molecular weight distribution, a method of blending SBR with extremely different average molecular weights (Mooney viscosity) can be considered, but the effect of the present invention is exhibited. To do so, it is essential to use n-octyl mercaptan as an essential component of the molecular weight regulator. In general, SBR by an emulsion polymerization method is widely industrially produced, but a tertiary dodecyl mercaptan (hereinafter abbreviated as t-DM) is generally used as a molecular weight regulator.
Is used. This is because the life as a molecular weight regulator during polymerization is long, and the Mooney viscosity can be controlled accurately with a small amount. In this case, the molecular weight distribution is relatively sharp, and the molecular chains are also linear.

When SBR by this ordinary polymerization method is applied as an asphalt modifier, physical properties of asphalt and workability (workability) have a trade-off relationship. In other words, if the Mooney viscosity of SBR is increased, asphalt physical properties such as grasping power of rubber-containing asphalt with aggregate (hereinafter referred to as "toughness") and adhesive strength to aggregate (hereinafter referred to as "tenacity") are improved, Asphalt viscosity at high temperature increases, and workability (workability) deteriorates. Conversely, if the Mooney viscosity of SBR is reduced, the workability is improved, but the asphalt properties such as toughness and tenacity are not sufficiently improved.

On the other hand, when the n-octyl mercaptan of the present invention is used as a molecular weight regulator and SBR having an extremely wide molecular weight distribution having a certain amount or more of a low molecular weight component and a high molecular weight component is blended into asphalt, surprisingly, It has been found that asphalt physical properties such as toughness and tenacity can be significantly improved while keeping the high-temperature viscosity, which is an index of properties, low.

As a method for obtaining an SRB having a low molecular weight component and a high molecular weight component of a certain amount or more and having a wide molecular weight distribution, a method of blending a high Mooney viscosity SBR and an extremely low Mooney viscosity SBR having extremely different average molecular weights (Mooney viscosity), etc. However, in this case, even if normal SBRs using t-DM as a molecular weight regulator are blended with each other, the balance between asphalt performance and workability only moves on the additive line of these SBRs. The improvement effect was not recognized so much.
That is, in order to exhibit the effects of the present invention, it is essential to use n-octyl mercaptan as an essential component of the molecular weight regulator.

Although the reason why SBR using n-octyl mercaptan exhibits a different behavior from SBR using normal t-DM is not clear, it is thought to be due to the difference in reactivity of mercaptan which is a molecular weight regulator. Can be

The amount of this n-octyl mercaptan added depends on the amount of the monomer.
The range of 0.05 to 5.0 parts by weight per 100 parts by weight is preferred. 0.
If the amount is less than 05 parts by weight, the effect of addition is small, and the low molecular weight component becomes less than a certain amount, so that asphalt workability deteriorates.
On the other hand, when the amount exceeds 5.0 parts by weight, the low molecular weight component is excessively increased, and the asphalt performance balance is deviated. The addition method may be any of batch addition, divided addition, and continuous addition. If the molecular weight distribution is within the above range, other molecular weight regulators such as t-DM may be used in combination.

The effect of the SBR used in the present invention is exhibited when it contains a certain or more low molecular weight component and a high molecular weight component. Specifically, a component having a molecular weight of 4.5 × 10 ⁴ or less
It is necessary to contain 15% by weight or more and 5.0 × 10 ⁵ or more components in an amount of 30% by weight or more. 4.5 as low molecular weight component
If the content of × 10 ⁴ or more is less than 15% by weight, the high temperature viscosity of the rubber-containing asphalt increases, and the workability (workability) deteriorates. When the amount of the polymer component of 5.0 × 10 ⁵ or more is less than 30% by weight, the effect of modifying asphalt physical properties such as toughness and tenacity is not sufficient. That is, the effect of the present invention is sufficiently exhibited only when both the low molecular weight component and the high molecular weight component are contained in a certain amount or more.
If this range is satisfied, SBR polymerized using only normal t-DM may be used as a blend with SBR polymerized using n-octyl mercaptan, but the ratio is 70% in order to exhibit the effect. Must be less than% by weight.

The SBR used in the present invention has an amount of bound styrene of 10 to 35.
If it is less than 10% by weight, it tends to gel when mixed with asphalt, and if it exceeds 35% by weight, rubber elasticity decreases.

Mooney viscosity is M from asphalt physical properties and workability
_{L1 + 4} Must be in the range of 50-140 at 100 ° C.

The SBR of the present invention can be added to asphalt as a latex state or a solid rubber, but is usually added in a latex state. The amount of SBR added to asphalt is in the range of 1 to 10 parts by weight of the SBR of the present invention as a solid component based on 100 parts by weight of asphalt depending on the type of asphalt used, traffic volume, and the like. In particular, when high fluid resistance, abrasion resistance, and crack resistance are required as in heavy traffic road pavement, it is preferable to add 3 to 10 parts by weight. Of course, other modifiers such as resin may be used in combination.

The asphalt pavement composition is obtained by mixing the above asphalt composition with aggregates of crushed stone, sand and stone powder, and is produced by a usual production method, for example, in an asphalt plant mixer.
It is manufactured by a plant mix method in which SBR latex is kneaded together with asphalt and aggregate, or a premix method in which aggregate is mixed with asphalt in which SBR is previously blended.

The particle size and mixing ratio of crushed stone, sand and stone powder of the aggregate can be appropriately selected according to a conventional method according to the purpose of pavement, and the amount of the asphalt composition is generally about 3 to 9% by weight of the composition in the pavement. 4.5-7.5% by weight is most common.

(Examples) Hereinafter, the present invention will be specifically described with reference to examples.

[1] Evaluation as a binder (Examples 1 to 4, Comparative Examples 1 to 4) (Example 1) A capacity of 100 according to the basic polymerization recipe shown in Table 1.
Was added to 71 parts of 1,3-butadiene, 29 parts of styrene, and 1.6 parts of n-octylmercaptan as a molecular weight regulator, and emulsion polymerization was started at a temperature of 5.5 ° C. When the conversion reached 58%, the reaction was stopped by adding 0.05 parts of diethylhydroxylamine. Next, the unreacted monomer was recovered and concentrated according to a conventional method to obtain an SBR latex having a solid content of 50%.

Use this latex as straight asphalt (with a penetration of 60
To 80, Showa Shell Sekiyu KK) at a temperature of 160 to 170 ° C to obtain a rubber-containing asphalt containing 3% of rubber in terms of solid content.

The following items were tested for this rubber-containing asphalt. Table 2 shows the evaluation results.

(A) Penetration Measurement was performed in accordance with JIS K2530. However, temperature 25
° C, a load of 100 g, and a load application time of 5 seconds.

(B) Softening point Based on JIS K2531.

(C) Toughness and tenacity were measured by the Benson method. However, the temperature was 25 ° C., the tension speed was 500 mm / min, and the tension amount was 30 cm.

(D) Viscosity at 60 ° C. Measured with a reduced pressure capillary viscometer according to JAA-001 (JAA: Japan Asphalt Association Test Method).

(E) 160 ° C., 180 ° C. Viscosity Measured using a BROOKFIELD type viscometer according to ASTM D2669.

In addition, in Table 2, the test method regarding the property of rubber latex is as follows.

(A) Bound styrene content Measured according to JIS K6387.

(B) Mooney viscosity ( _{ML1 + 4} , 100 ° C) The rubber component is recovered from rubber latex, and the rubber is JISK
Measured according to 6383.

(C) Molecular weight As described above.

(Example-2) The procedure of Example-1 was followed except that the amount of n-octyl mercaptan added was changed to 0.2 part.

Example 3 A molecular weight modifier was combined with 0.35 part of n-octyl mercaptan.
Example 1 was repeated except that 0.06 parts of tertiary dodecyl mercaptan (t-DM) was used in combination.

(Example-4) SBR latex (Mooney viscosity _{ML1 +} 498) polymerized according to Example-1 using 0.70 part of n-octylmercaptan as a molecular weight regulator and 0.20 part of t-dodecylmercaptan were used. 1: 1 blend with latex-polymerized SBR latex (Moony viscosity M _{L1 +} 450) (latex blend)
Example 1 was repeated except that the used latex (Mooney viscosity _{ML1 +} 473) was used.

(Comparative Example 1) The procedure of Example 1 was followed, except that the molecular weight modifier was changed to 0.285 parts of t-dodecyl mercaptan.

(Comparative Example 2) Example 1 was repeated except that the molecular weight modifier was changed to 0.20 part of t-dodecyl mercaptan.

(Comparative Example 3) The same operation as in Example 1 was conducted except that the molecular weight modifier was changed to 0.08 part of t-dodecyl mercaptan.

(Comparative Example -4) Comparative Example -2 and SBR Ratekkuku used in Comparative Example 3 (each, Mooney viscosity M _{L1 + 4} 50 and 151) 1: Latex blended SBR latex 1 (Mooney viscosity M _{L1 + 4} Example 1 was followed except that 97) was used.

[2] Evaluation as a mixture (Examples 5 to 7, Comparative Examples 5 to 7) (Example-5) 5 parts by weight of the rubber-containing asphalt obtained in Example-1 and an aggregate (5 No. 6 crushed stone, No. 6 crushed stone, No. 7 crushed stone, 95 parts by weight of a mixture of coarse sand, fine sand and stone powder) were mixed at a temperature of 170 to 180 ° C. to obtain a dense-grained asphalt concrete mixture. This mixture was compacted at 170 ° C. 75 times each on both sides, and a marshall stability test was performed in accordance with the asphalt pavement guidelines. Table 4 shows the evaluation results.

(Example-6) According to Example-5 except that the asphalt composition obtained in Example-2 was used as the asphalt containing rubber.

(Example-7) The procedure of Example-5 was followed except that the asphalt composition obtained in Example-4 was used as the asphalt containing rubber.

(Comparative Example-5) Example 5 was followed except that the asphalt composition obtained in Comparative Example-2 was used as the rubber-containing asphalt.

(Comparative Example-6) The same operation as in Example-5 was performed except that the asphalt composition obtained in Comparative Example-3 was used as the rubber-containing asphalt.

(Comparative Example-7) 5 parts by weight of straight asphalt (penetration of 60 to 80, manufactured by Showa Shell Sekiyu KK) and aggregates shown in Table 3 (crushed stone No. 5, crushed stone No. 6, crushed stone No. 7, coarse sand) , A mixture of fine sand and stone powder) at a temperature of 150 to 160 ° C. to obtain a dense-grained asphalt concrete mixture.

This mixture was compacted at 145 ° C. 75 times on both sides, and a marshall stability test was performed according to the asphalt pavement guidelines. The evaluation results are shown in Table 4.

*) Stiffness is the value obtained by dividing the stability by the flow value (S /
F), and according to the results of a nationwide survey on plastic flow of asphalt pavement conducted by the Ministry of Construction ¹⁾ , it is shown to be relatively correlated with rutting.

1) Report of the 32nd Research Meeting of the Ministry of Construction, Civil Engineering Research Center, pp. 217-234, October 1979 (Effects of the Invention) Asphalt compositions containing the rubber latex of the present invention as described above are toughness, While asphalt performance such as tenacity is greatly excellent, high-temperature viscosity, which is an index of workability (workability), can be kept low.
It can be seen that the balance between asphalt performance and workability, which were contrary to each other, has been greatly improved. Further, the marshalling stability and stiffness of the pavement mixture are high, and when the pavement is actually constructed, the workability is good, and a road excellent in rutting resistance and abrasion resistance is obtained.

[Brief description of the drawings]

FIG. 1 shows a typical molecular weight distribution of the SBR latex used in Examples and Comparative Examples. The molecular weight distribution of the SBR latex of the present invention using n-octyl mercaptan as the molecular weight regulator is the same as that of the conventional SBR latex using t-dodecyl mercaptan.
It is extremely broad compared to SBR latex. FIG. 2 and FIG. 3 are graphs in which toughness and tenacity, which are indexes of asphalt performance, and asphalt high-temperature viscosity (180 ° C.), which is an index of workability (workability), are plotted.

Claims (2)

(57) [Claims] (1) A styrene-butadiene copolymer obtained by emulsion polymerization of 0.05 to 5.0 parts by weight of n-octyl mercaptan as an essential component of a molecular weight modifier, based on 100 parts by weight of a monomer, and at least 30% by weight or more, (B) 15% by weight or more of a component having a molecular weight of 4.5 × 10 ⁴ or less and 30% by weight or more of a component having a molecular weight of 5.0 × 10 ⁵ or more. The amount of bound styrene satisfying the above conditions (a) and (b) is 10 to
A styrene-butadiene copolymer having a Mooney viscosity (ML1 _{+ 4} , 100 ° C) in the range of 50 to 140% by weight, asphalt
An asphalt composition comprising 1 to 10 parts by weight per 100 parts by weight. 2. An asphalt pavement composition comprising a mixture of the asphalt composition according to claim 1 and an aggregate.