CN116323805A

CN116323805A - Process for producing asphalt composition and process for producing asphalt mixture

Info

Publication number: CN116323805A
Application number: CN202180070505.3A
Authority: CN
Inventors: 石崎雅也; 宫胁正一; 辻志穗; 渡边清隆; 山田敏广; 青木政树
Original assignee: Japan Dacheng Road Technology Co ltd; Nippon Paper Industries Co Ltd
Current assignee: Japan Dacheng Road Technology Co ltd; Nippon Paper Industries Co Ltd
Priority date: 2020-10-19
Filing date: 2021-10-18
Publication date: 2023-06-23
Also published as: WO2022085641A1; JPWO2022085641A1

Abstract

The invention provides a method for producing an asphalt mixture, which can improve the stability. In order to solve the technical problem, a method for producing an asphalt mixture using an asphalt composition containing lignin and asphalt, comprises: a 1 st mixing step S1 of mixing lignin having a glass transition temperature of lignin, that is, a predetermined temperature or lower, with pitch having the predetermined temperature or lower; a holding step S2 of holding the mixture at the predetermined temperature or lower for a predetermined time after the 1 st mixing step S1; and a 2 nd mixing step S3 of mixing at least the asphalt composition obtained in the 1 st mixing step S1 and the holding step S2 with the aggregate.

Description

Process for producing asphalt composition and process for producing asphalt mixture

Technical Field

The present invention relates to a method for producing an asphalt composition and a method for producing an asphalt mixture.

Background

A new method of utilizing lignin extracted from wood is being studied. Patent document 1 describes a technique in which lignin can be added to asphalt in paragraph 0032.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2004-143243

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors studied and found that the addition of lignin alone to asphalt may decrease the stability of the resulting asphalt composition and asphalt mixture, and the details will be described by way of examples.

The invention aims to provide a method for manufacturing an asphalt composition and a method for manufacturing an asphalt mixture, which can improve stability.

Effects of the invention

According to the present invention, a method for producing an asphalt composition and a method for producing an asphalt mixture, which can improve the stability, can be provided.

Drawings

FIG. 1 is a flow chart showing a method for producing an asphalt composition and a method for producing an asphalt mixture.

Fig. 2 is a graph obtained by further adding the results of the marshall stability test of the reference example to fig. 2.

Fig. 3 is a graph obtained by further adding the stability of the reference example to fig. 2.

Fig. 4 is a graph showing the difference in durability of the content ratio of pitch mixture to kraft lignin.

Detailed Description

Hereinafter, an embodiment (referred to as an embodiment) for carrying out the present invention will be described with reference to the drawings. In the following description of one embodiment, description of another embodiment applicable to one embodiment is also appropriately made. The present invention is not limited to the following embodiment, and various embodiments may be combined with each other or may be arbitrarily modified within a range that does not significantly affect the effects of the present invention. The same reference numerals are given to the same components, and duplicate descriptions are omitted. Also, components having the same function are given the same names. The illustrated content is merely illustrative, and may be modified according to the actual configuration within a range that does not significantly affect the effects of the present invention, or some of the components may be omitted from the drawings or modified.

FIG. 1 is a flow chart showing a method for producing an asphalt composition and a method for producing an asphalt mixture. The asphalt mixture may be manufactured using an asphalt composition comprising lignin and asphalt. The method for producing the asphalt composition includes a 1 st mixing step S1 and a holding step S2.

In addition, the asphalt mixture comprises lignin, asphalt and aggregate, further comprising a suitable filler. The method for producing the asphalt mixture includes a raw material mixing step S4 in which lignin, asphalt, aggregate, and an appropriate filler are mixed in a state in which the glass transition temperature of the lignin is equal to or lower than a predetermined temperature. The raw material mixing step S4 includes a 2 nd mixing step S3, and for example, at least the asphalt composition and the aggregate produced in the 1 st mixing step S1 are mixed (the appropriate filler may be further mixed). However, the 1 st mixing step S1 and the 2 nd mixing step S3 may be performed simultaneously, and specifically, in the raw material mixing step S4, lignin, asphalt, aggregate, and an appropriate filler may be mixed simultaneously in the same system.

The 1 st mixing step S1 is a step of mixing lignin and pitch. Lignin is mixed in a state of being preheated to a temperature equal to or lower than the glass transition temperature (hereinafter, appropriately abbreviated as a predetermined temperature) of itself (lignin itself to be mixed). Asphalt is also mixed while being preheated to a temperature equal to or lower than the predetermined temperature.

The glass transition temperature of lignin is considered to be different depending on the kind of wood from which lignin is extracted (for example, the difference between broad-leaved trees and conifers, and the kinds of pine, fir, and the like are classified even in the same conifer). The glass transition temperature of lignin which can be used is not particularly limited, and is, for example, 100℃or higher, preferably 110℃or higher, more preferably 120℃or higher, particularly preferably 140℃or higher, and the upper limit is, for example, 200℃or lower, preferably 190℃or lower, more preferably 180℃or lower, particularly preferably 165℃or lower.

The glass transition temperature of lignin can be measured, for example, by thermo-mechanical analysis (TMA). The thermal mechanical analysis method detects a change in displacement or pressure due to a change in temperature, and the analysis method may be performed using a thermal mechanical analysis device (e.g., TMA8310L manufactured by phylogenetic company). For example, the above-mentioned apparatus can be used to analyze lignin powder at 3 to 5mg, nitrogen gas at 150 mL/min, load at 49mN, initial temperature at 50℃and end temperature at 250℃at a heating rate of 2℃per minute. In the temperature increase process, for example, a temperature at which the expansion coefficient abruptly changes may be used as the glass transition temperature.

By mixing lignin and asphalt separately at a temperature equal to or lower than the predetermined temperature, the stability of the asphalt composition and the asphalt mixture can be improved.

The mixing ratio of lignin and pitch is not particularly limited. However, in the 1 st mixing step S1, the lignin and the pitch are preferably mixed so that the lignin is more than 0 parts by mass and 50 parts by mass or less based on 100 parts by mass of the total of the lignin and the pitch. When the mixing ratio is within this range, the function of asphalt can be easily exhibited.

Among them, the upper limit of the mixing ratio of lignin is more preferably 30 parts by mass or less. The porosity and saturation of the asphalt mixture can be improved by setting the mixing ratio to 30 parts by mass or less.

Further, the upper limit of the mixing ratio of lignin is more preferably 10 parts by mass or less. When the mixing ratio is 10 parts by mass or less, lignin and asphalt can be sufficiently covered with the aggregate in the production of the asphalt mixture, and the details will be described later.

The lower limit is, for example, 5 parts by mass or more.

The specific method for mixing lignin and pitch is not particularly limited, as long as lignin at the above-mentioned predetermined temperature or lower and pitch at the above-mentioned predetermined temperature or lower can be mixed. For example, pitch may be added while stirring lignin with a mixing device (dry mixing), or lignin may be added while stirring pitch with a mixing device (wet mixing). In addition, lignin and pitch may be fed into the mixing device simultaneously. Through the full stirring operation, the pitch and lignin are circulated within the mixing device.

In the 1 st mixing step S1, it is preferable to mix lignin having a temperature equal to or lower than the predetermined temperature while stirring asphalt having the temperature equal to or lower than the predetermined temperature with a mixing device. By doing so, aggregation of lignin can be suppressed, and lignin can be uniformly mixed in the whole asphalt. The mixing device is not particularly limited, and any mixing device may be used, for example, an asphalt mixer may be used.

Preferably, the temperature of the asphalt is 60 ℃ or higher. By setting the temperature of the asphalt to 60 ℃ or higher, the curing of the asphalt can be suppressed, and lignin can be dispersed in the asphalt. Therefore, it is preferable that the pitch is mixed with lignin at a temperature equal to or lower than the predetermined temperature and preheated to, for example, 60 ℃.

The temperature of lignin is not particularly limited, and may be equal to or lower than the temperature of the mixed asphalt or equal to or higher than the temperature of the mixed asphalt.

The mixing device is preferably used in a state where the temperature of the mixed asphalt is equal to or lower than the predetermined temperature and the temperature is equal to or higher than the predetermined temperature. This can prevent lignin and asphalt from exceeding a predetermined temperature in the mixing device, and can prevent asphalt from solidifying due to a decrease in temperature.

The 1 st mixing step S1 is preferably performed in an open system. Since lignin and pitch are mixed at the above predetermined temperature or lower, decomposition of lignin can be suppressed, and generation of hydrogen sulfide during mixing can be suppressed. Therefore, the 1 st mixing step S1 can be performed in an open system, and a mixing apparatus having a simple structure can be used.

The specific types of lignin and pitch are also not particularly limited. However, it is preferred that the lignin comprises kraft lignin, wherein a dry matter comprising kraft lignin is more preferred. Asphalt compositions and asphalt mixtures can be easily manufactured because of the ready availability of the dried kraft lignin. In addition, lignin is preferably mixed in the form of powder. By mixing in the powder state, lignin and pitch can be easily fused. However, lignin is not limited to dry lignin, and may be water-containing lignin (e.g., wet lignin, slurry, etc.) which is a lignin containing moisture. By using an aqueous lignin, the lignin can be dried during the mixing process inside the mixing device, and the drying time can be omitted, details of which will be described later.

Preferably, the bitumen comprises straight-run bitumen. By including straight asphalt, durability against traffic vehicles can be improved, for example, when paving using an asphalt mixture. However, the asphalt may be modified asphalt.

Preferably, the asphalt comprises asphalt recycled aggregate. Asphalt recycled aggregate is, for example, asphalt that causes cracks, ruts, and other deformations in the asphalt being laid, and can be produced by stripping and appropriately pulverizing such asphalt. The amount of asphalt used can be reduced by producing an asphalt composition and an asphalt mixture using the asphalt recycled aggregate.

In the mixing step S1, any component other than lignin and pitch may be used within a range that does not significantly affect the effect of the present invention.

The holding step S2 is a step of holding the mixture at the predetermined temperature or lower for a predetermined time after the 1 st mixing step S1. By including the holding step S2, the asphalt composition can be cured, and an asphalt composition in which lignin and asphalt are sufficiently fused can be obtained. However, the holding step S2 may be omitted.

The holding step S2 is performed by keeping the temperature at or below the predetermined temperature, and the temperature may not be kept at a constant temperature as long as the temperature is at or below the predetermined temperature. The lower limit of the holding temperature is not particularly limited, and may be 60℃or higher, for example. The heat preservation can be performed by any heat preservation device.

The predetermined time for carrying out the holding step S2 is not particularly limited, and may be, for example, 30 minutes to 24 hours. The holding step S2 may be performed while being left to stand or may be performed while stirring. Wherein, the time of the holding step S2 can be shortened by stirring.

The stirring may be performed using any stirring device.

The asphalt composition is obtained through at least the above 1 st mixing step S1 (an example of the raw material mixing step S4), and the asphalt mixture is obtained through the 2 nd mixing step S3 (an example of the raw material mixing step S4).

The 2 nd mixing step S3 is a step of mixing at least the asphalt composition prepared in the 1 st mixing step S1 with the aggregate. By passing through the 2 nd mixing step S3, an asphalt mixture can be produced. The aggregate is, for example, sand, stone, gravel or the like having a diameter of 1mm or more. The amount of the aggregate to be used is not particularly limited, and for example, the aggregate can be used in a ratio of 1000 parts by mass or more and 10000 parts by mass or less based on 100 parts by mass (total mass of asphalt and lignin) of the asphalt composition.

The pitch composition contains lignin as described above, and lignin generally functions as a filler (or a binder (a binder such as a thermosetting resin)) in the pitch mixture. Thus, the asphalt mixture comprises at least asphalt, for example lignin and aggregate as filler. In the raw material mixing step S4, the use of a filler (for example, an inorganic powder) that is generally used may be omitted, but as described above, a general filler may be used alone. In the raw material mixing step S4, when the filler is further mixed, the filler is preferably mixed so that the filler is, for example, 50 parts by mass or less, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, with respect to 100 parts by mass of the mixture of lignin and the filler, as a lower limit. The gaps between the aggregates can be filled or the aggregates can be coated by a mixture of asphalt and filler (filler asphalt). Thus, the density and stability can be improved.

The specific kind of filler used is arbitrary, and for example, stone powder obtained by pulverizing limestone can be used, but is not limited thereto.

The specific conditions for mixing the asphalt composition and the aggregate are not particularly limited. However, in the 2 nd mixing step S3, it is preferable to mix the aggregates preheated to the predetermined temperature or lower in the asphalt composition preheated to the predetermined temperature or lower. By doing so, lignin and asphalt can be easily fused with aggregate. In the case of using other components (another filler, etc.), the same is preferable.

In another embodiment, the 1 st mixing step S1 and the 2 nd mixing step S3 are performed simultaneously as described above, whereby lignin, asphalt, aggregate, and the filler are mixed simultaneously in the same system. In this case, the descriptions (the use amount, the mixing temperature, etc.) regarding lignin, asphalt, aggregate, and an appropriate filler can be similarly applied to the respective descriptions regarding the 1 st mixing process S1 and the 2 nd mixing process S3. For example, in the raw material mixing step S4, lignin and pitch may be mixed so that the lignin is greater than 0 parts by mass and 50 parts by mass or less relative to 100 parts by mass of the total of lignin and pitch.

In still another embodiment, in the raw material mixing step S4, for example, the aqueous lignin containing lignin and water is mixed with the aggregate having a temperature equal to or higher than the predetermined temperature by a mixing device so that lignin is maintained at a temperature equal to or lower than the predetermined temperature. By doing so, the moisture in the hydrous lignin can be evaporated by the heat of the aggregate. This can dry lignin in the mixing apparatus, and can reduce the drying work before mixing. Further, the water content of lignin, the amount of other components used, the temperature, and the like are preferably determined so that the temperature of the mixing device (particularly lignin) is maintained at or below the glass transition temperature.

The asphalt mixture produced is used as a water-blocking material for, for example, laying on roads and the like, roof waterproofing, dams, airport runways and the like. The asphalt mixture produced is easy to adhere to the existing concrete, and therefore has good workability. In addition, in the Marshall stability test, the ratio of the maximum load shown until the sample breaks to the deformation amount relative to the maximum load is 1.7MPa/mm or more for the asphalt mixture to be produced. This can improve the strength of the asphalt mixture. Furthermore, the marshall stability test can be as follows: the method described in "society legal Japanese road society, B0001 Marshall stability test method, laying research and test Manual [ division 3] (19 years, 6 months, p.5-15)".

In addition, the bituminous mixture of the present invention contains lignin derived from wood that has absorbed carbon dioxide from the atmosphere. Therefore, carbon derived from carbon dioxide in the atmosphere is fixed by, for example, laying, and the amount of carbon dioxide in the atmosphere can be reduced. Thus, the reduction of the amount of carbon dioxide in the atmosphere and the installation of foundation facilities by laying or the like can be simultaneously achieved, and the objective 13' of the sustainable development objective (SDGs (Sustainable Development Goals)) [ climate change ] can be performed, and emergency countermeasures for reducing the climate change and the influence thereof can be taken. The wood used is able to perform the protection, restoration, sustainable utilization propulsion, sustainable forest management, prevention/restoration of coping with desertification and land degradation and loss of prevention biodiversity "of the target 15" [ land resources ] land area ecosystem and the target 12"[ sustainable consumption and production ] by combining forestation and deforestation cycles, ensuring sustainable consumption production morphology).

Examples

Example 1 >

Asphalt compositions and asphalt mixtures were prepared according to the flow chart shown in fig. 1, and the performance was evaluated.

The kraft lignin powder was made by the following method. First, kraft lignin dispersed as a polymer in black liquor was extracted by filtration, and dried sufficiently in a drying oven at 50 ℃ to obtain a kraft lignin dried product having a water content ratio of 0. Next, the dried product was sufficiently pulverized to obtain a powder passing through a sieve having a mesh size of 0.0075 mm. The powder is a dry powder of kraft lignin.

The glass transition temperature was determined by the thermo-mechanical analysis described above for the dry powder of kraft lignin. As a result, the glass transition temperature was 161 ℃.

Subsequently, pitch and lignin were mixed by the following method (mixing step S1 (fig. 1)). 2000g of asphalt (petroleum asphalt for pavement/straight asphalt pen60-80; straight asphalt) preheated to a glass transition temperature (161 ℃) of 160 ℃ or lower, which is the glass transition temperature of the kraft lignin after mixing, was charged into a mixing apparatus having stirring blades, and mixed while circulating inside the mixing apparatus. The mixing device was set to be capable of mixing at 160℃and was a device capable of mixing in an open system in which the inside and the outside of the mixing device communicate. Then, 2000g of a dry powder of kraft lignin at normal temperature (20 ℃) was charged in an amount of 100g per 1 minute (relative to 100 parts by mass of the total of lignin and pitch, lignin: pitch=50:50), and after all charging, the mixture was mixed while keeping the temperature at 160℃for 1 hour.

After 1 hour, the mixing was stopped, and the mixture was left to stand at 160℃for 12 hours (holding step S2). After 12 hours, the mixture was taken out of the mixing apparatus to obtain an asphalt composition.

71.2g of the asphalt composition taken out of the mixing apparatus was preheated to 160℃and 1200g of aggregate which had been preheated to 160℃and mixed for 60 seconds was charged into the mixing apparatus in the whole of 1 minute, and after the charging, the mixture was mixed while being circulated for 180 seconds (mixing step S3 of the 2 nd). The mixing device used for mixing is set to be capable of mixing at 160℃in the same manner as the mixing device used for producing the asphalt composition, and is a device capable of mixing in an open system in which the inside of the mixing device communicates with the outside. After 180 seconds, the mixing was stopped and removed from the mixing device, thereby obtaining an asphalt mixture. The same operation was repeated for the asphalt mixture to prepare 3 asphalt mixtures (n=3). In addition, an asphalt mixture was prepared by scaling up 712g of asphalt composition and 12000g of aggregate so that the ratio of the asphalt-containing composition was the same (7.6 mass%).

The above-mentioned asphalt composition and asphalt mixture were produced by providing a hydrogen sulfide concentration measuring device (XS-2200, manufactured by COSMOS electric company, new) in the vicinity of the mixing device, and measuring the concentration of hydrogen sulfide. As a result, in the production process, hydrogen sulfide was not more than the detection threshold, and no generation of hydrogen sulfide was confirmed.

Example 2 >

An asphalt mixture was produced in the same manner as in example 1, except that the amount of lignin used was 7.12g and the amount of asphalt used was 64.08g (lignin 10 parts by mass: asphalt=10:90, based on 100 parts by mass of the total of lignin and asphalt). The same operation was repeated for the asphalt mixture to prepare 3 asphalt mixtures (n=3). In the production of the asphalt composition and the asphalt mixture, the hydrogen sulfide was not more than the detection limit, and no generation of hydrogen sulfide was confirmed. The same applies to the case where the mass of the asphalt composition and the aggregate is scaled up to 1t in total.

Example 3 >

An asphalt mixture was produced in the same manner as in example 1, except that the amount of lignin used was 21.36g and the amount of asphalt used was 49.84g (lignin: 30 parts by mass, lignin: asphalt=30:70, based on 100 parts by mass of the total of lignin and asphalt). The same operation was repeated for the asphalt mixture to prepare 3 asphalt mixtures (n=3). In the production of the asphalt composition and the asphalt mixture, the hydrogen sulfide was not more than the detection limit, and no generation of hydrogen sulfide was confirmed. The same applies to the case where the total of the asphalt composition and the aggregate is scaled up to 10 kg.

Comparative example 1 >

An asphalt composition and an asphalt mixture were produced in the same manner as in example 1, except that the setting temperature and the preheating temperature of the mixing apparatus were 185 ℃ instead of 160 ℃. In comparative example 1, the hydrogen sulfide concentration was measured and the production was performed. As a result, no hydrogen sulfide was observed to be generated during the production process.

< evaluation of Performance >

The Marshall stability test was performed on the asphalt mixtures of example 1 and comparative example 1, and performance evaluation concerning stability was performed. The Marshall stability test was performed according to the method described in the above-mentioned document. The results are shown in fig. 2.

FIG. 2 is a graph showing the results of the Marshall stability test of example 1 and comparative example 1. The vertical axis represents the stability (kN) as measured by the marshall stability test. The greater the value representing the degree of stability, the more stable the asphalt mixture. The asphalt mixture of example 1 had a stability of 13.9kN and the asphalt mixture of comparative example 1 had a stability of 10.8kN. Therefore, it was found that the asphalt mixture of example 1 produced at a temperature lower than the glass transition temperature of lignin was higher in stability than the asphalt mixture of comparative example 1 produced at a temperature exceeding the glass transition temperature of lignin.

Fig. 3 is a graph obtained by further adding the results of the marshall stability test of the reference example to fig. 2. A asphalt mixture was produced in the same manner as in example 1, except that only asphalt was used instead of lignin, and a marshall stability test was performed in the same manner as in example 1. The bitumen mixture of the reference example has a stability of 13.85kN.

The asphalt mixture of example 1, which was prepared below the glass transition temperature of lignin, had the same stability as the asphalt mixture of the reference example, which used only asphalt and not lignin. This is considered to be because the lignin is uniformly dispersed in the asphalt mixture by stirring the mixture with a mixing device at a temperature equal to or lower than the glass transition temperature of the lignin, thereby improving the stability (maintaining the same level as that of straight asphalt).

However, the asphalt mixture of comparative example 1, which was produced at a temperature exceeding the glass transition temperature of lignin, had a stability about 20% lower than that of the asphalt mixture of the reference example. The reason is considered that the temperature of lignin charged into the mixing apparatus increases to exceed the glass transition temperature, and changes in characteristics such as hydrogen sulfide generation are caused. As a result, in comparative example 1, it is considered that the lignin having characteristics different from those of the lignin of example 1 in a state where the glass transition temperature is not reached, and thus the stability is lowered (the effect of functioning as straight asphalt is low).

As other properties, durability of the content ratio of the asphalt mixture to kraft lignin was evaluated for examples 1 to 3 and reference examples. As an index of durability, dynamic Stability (DS) was evaluated. The evaluation of dynamic stability was performed according to the methods described in "society of Japan road Association, B0003, lt track test method, manual of laying research/test method [ division 3], 19 years 6 months, p.39-56".

Fig. 4 is a graph showing the difference in durability of the content ratio of pitch mixture to kraft lignin. The vertical axis of fig. 4 shows dynamic stability, and shows that the larger the number, the higher the durability. Dynamic stability is 3653 in example 1, 1115 in example 2, 2640 in example 3, and 760 in the reference example.

Asphalt mixtures of examples 1-3 were all made below the glass transition temperature of lignin. Therefore, when the asphalt mixture is produced at a temperature equal to or lower than the glass transition temperature of lignin, the asphalt mixture has higher durability than that of the asphalt mixture of the reference example in which lignin is not used. The reason is considered to be that, as in the above-described examination in fig. 3, the lignin is uniformly dispersed in the asphalt mixture by stirring with a mixing device, thereby improving the stability (maintaining the same level as that of straight asphalt).

In the asphalt mixtures of examples 1 to 3, the higher the lignin content, the higher the dynamic stability was. This is thought to be because the higher the lignin content ratio, the more lignin polymer groups having a smaller relative molecular weight are contained in the polymer groups constituting lignin, which are melted at a lower temperature. The lignin polymer group having a small relative molecular weight functions as a thermosetting resin by melting. Further, it is considered that slag generated by melting has a modifying effect on straight asphalt, and the dynamic stability of the asphalt mixture is improved. This effect can be exerted by adjusting the temperature at the time of mixing so as to suppress the generation of hydrogen sulfide due to the decomposition of lignin.

Table 1 below is a table illustrating the difference in behavior of lignin of different relative molecular weights for each lignin polymer group (so-called normal lignin) when the glass transition temperature measured by a thermo-mechanical analysis method is, for example, 150 ℃.

TABLE 1

Table 1: the glass transition temperature (Tg) measured was 150℃in the case (envisaged)

The glass transition temperature of lignin is assumed to be different depending on the relative molecular weight, and for example, the higher the relative molecular weight is, and the lower the relative molecular weight is, the lower the relative molecular weight is. The glass transition temperature, measured for example by thermomechanical analysis, can be said to be the average value, comprising lignin of different relative molecular weights. However, for example, by measuring the glass transition temperature by a thermo-mechanical analysis method and mixing the above materials at or below the measured value of the glass transition temperature measured by the thermo-mechanical analysis method, thermal degradation can be suppressed even in any lignin having a small or large relative molecular weight. Thus, the solid lignin produced by cooling the melt can be left in the asphalt mixture, thereby exhibiting the effect of the present invention.

As a further property, porosity and saturation were calculated for the bituminous mixtures of examples 1 to 3. The porosity is calculated according to the following formula (1), and the saturation is calculated according to the following formula (2). Saturation is the percentage of straight asphalt in the interstices of the aggregate. The results are shown in table 1 below.

v=vv/v×100= (1- ρm/D) ×100× 100 … (1)

The target value v is the porosity (%), ρm is the density (g/cm) of the asphalt mixture ³ ) V is the volume of the asphalt mixture (cm ³ ) Vv is the void volume (cm) in the asphalt mixture ³ )。

s=va/(V-Vag) ×100=va/(va+v) ×100 … (2)

The target value s is saturation (%), va is volume percentage (%) of asphalt, and Vag is aggregate volume (cm) in the asphalt mixture ³ ) V and V have the same meanings as V and V of formula (1).

Further, formulas (1) and (2) are literature: the formulas described in "society law Japanese road society, B0008, method for measuring density of asphalt mixture, laying research/test method handbook [ 3 rd handbook ], hei Cheng 19 years, 6 months, p.91-105".

TABLE 2

	Example 1	Example 2	Example 3
				Lignin (-)	50	10	30
Asphalt (-)	50	90	70
				Porosity v (%)	8.9	4.5	5.5
Saturation s (%)	59	74.9	70.7

In the case of using the asphalt mixture for a pavement, it is preferable that the asphalt mixture has a small porosity in order to suppress intrusion of rainwater. By reducing the porosity, the water permeability coefficient can be reduced. On the other hand, as shown in the above formula (2), the saturation is inversely related to the porosity. Therefore, when the porosity is reduced, the saturation can be increased. Therefore, as shown in examples 2 and 3, which have small porosity and large saturation, it is found that lignin is preferably more than 0 parts by mass and 30 parts by mass or less relative to 100 parts by mass of the total of lignin and pitch. By setting the range to be small in porosity and large in saturation, for example, an asphalt mixture suitable for a pavement can be obtained. The following reasons are considered.

The lignin polymer group contains lignin exhibiting a modifying effect having a small relative molecular weight and lignin dispersed in asphalt in a solid state other than the lignin polymer group, as described above with reference to table 1. The former lignin is lignin having a small relative molecular weight which melts at the glass transition temperature in table 3 below. On the other hand, the latter lignin is lignin having a relatively large molecular weight in the following table 3.

TABLE 3

Table 3: the glass transition temperature (Tg) measured was 150℃in the case (envisaged)

As described above, lignin functions as a filler in asphalt mixtures, for example, and by calculating the density, the filler functions as an aggregate. However, lignin after thermal degradation does not recover the function as lignin even when cooled, and therefore does not function as a filler. Therefore, by mixing at a temperature exceeding the glass transition temperature of lignin, the asphalt mixture contains lignin (lignin after thermal degradation) having a density smaller than that of aggregate, and the porosity increases by calculation due to the decrease in density.

Further, by mixing at or below the glass transition temperature of lignin and setting the lignin content to 30 parts by mass or less, the absolute amount of lignin having a small relative molecular weight can be reduced, and as a result, lignin that melts and thermally deteriorates can be reduced, and lignin itself existing in the asphalt mixture can be reduced. This reduces lignin present between aggregates, that is, lignin functioning as a filler, during compaction, and brings the aggregates closer to each other, thereby reducing the porosity. In addition, since the aggregate can be densified, the density is increased.

Further, as described above, the porosity is preferably reduced, but the porosity may be increased. For example, in order to improve visual confirmation in rainy days and to improve the skid resistance of a road surface, an asphalt mixture having a high drainage function and a large number of voids can be produced. Such asphalt mixtures can be used, for example, for paving highways, national roads, and the like.

Example 4 >

Asphalt compositions and asphalt mixtures containing fillers are made. Then, the marshall stability test (measurement of stability [ kN ]) and rutting track test (measurement of dynamic stability [ - ]) were performed on the produced asphalt mixture by the method described in the above < performance evaluation >, and the porosity and saturation were calculated.

An aqueous product of kraft lignin (aqueous lignin) different from example 1 was produced by the following method. First, kraft lignin dispersed as a polymer in black liquor is extracted by filtration, and aqueous lignin (wet lignin) is obtained. A portion of the aqueous lignin was collected and dried, and the glass transition temperature of the lignin was determined by the thermo-mechanical analysis method described above. As a result, the glass transition temperature was 168 ℃.

Subsequently, asphalt, aqueous lignin, filler (stone powder) and aggregate were simultaneously mixed by the following method (raw material mixing step S4 (fig. 1) in which mixing step S1 and mixing step S2 are simultaneously performed). The mixing was started by adding aggregates and fillers preheated to a temperature above the glass transition temperature of lignin (200 ℃) to a mixing device (same as in example 1) to which aqueous lignin had been added in advance. The mixing was performed for 100 seconds. In addition, when the mixture was mixed with the aqueous lignin, the temperature of the aggregate and the filler was lowered, and it was confirmed that the inside of the mixing apparatus was maintained at the glass transition temperature (168 ℃) of lignin or less during the mixing.

For each material, the amount of asphalt was 44kg, aqueous lignin was 50kg (of which lignin was 40 kg), filler was 25kg, and aggregate was 891kg. Therefore, in the raw material mixing step S4 (fig. 1), the filler is mixed so that the filler is 38.5 parts by mass (50 parts by mass or less) per 100 parts by mass of the mixture of lignin and the filler. The amount of lignin used was 47.6 parts by mass and the amount of aggregate used was 1060 parts by mass, based on 100 parts by mass of the total of lignin and pitch. Immediately after the completion of the mixing, the mixture was taken out of the mixing apparatus to obtain an asphalt mixture.

The stability [ kN ], dynamic stability [ - ], porosity and saturation were calculated for the asphalt mixture produced by the method described in the above < evaluation of properties >. As a result, the stability was 13.0kN, dynamic stability was 3150, porosity was 3.0% and saturation was 79.4%.

Example 5 >

In the 2 nd mixing step S3 (fig. 1), an asphalt mixture was produced in the same manner as in example 4, except that the filler was mixed so that the amount of the filler was 41.7 parts by mass (50 parts by mass or less) per 100 parts by mass of the mixture of lignin and the filler. The resulting asphalt mixture had a stability of 14.3kN, a dynamic stability of 7870, a porosity of 3.7% and a saturation of 75.8%.

Comparative example 2 >

The asphalt mixture of comparative example 2 was prepared in the same manner as in example 4, except that the asphalt of example 41 was used instead of lignin (i.e., the same amount of asphalt as used in lignin was used instead of lignin). The resulting asphalt mixture had a stability of 12.8kN, a dynamic stability of 4200, a porosity of 3.0% and a saturation of 80.0%.

As a result of comparing examples 4 and 5 with comparative example 2, it was found that even if a part of the filler was replaced with lignin, the physical properties of the asphalt mixture were not significantly affected. Among them, in regard to dynamic stability, example 5 was larger than comparative example 2, and performance was improved. In this way, it was confirmed that lignin acts as filler pitch in the pitch mixture, and the performance can be improved.

Description of the reference numerals

S1 st mixing procedure

S2 holding step

S3 No. 2 mixing procedure

S4 raw material mixing step

Claims

1. A process for producing a pitch composition comprising lignin and pitch, characterized in that,

comprises a 1 st mixing step of mixing the lignin having a glass transition temperature of the lignin, that is, a predetermined temperature or lower, with the pitch having the predetermined temperature or lower.

2. A process for producing an asphalt composition according to claim 1, wherein,

in the 1 st mixing step, the lignin having a temperature equal to or lower than the predetermined temperature is mixed while stirring the asphalt having a temperature equal to or lower than the predetermined temperature.

3. A process for producing an asphalt composition according to claim 1 or 2, wherein,

the temperature of the asphalt to be mixed is 60 ℃ or higher.

4. A process for producing an asphalt composition according to claim 1 or 2, wherein,

in the 1 st mixing step, the lignin and the pitch are mixed so that the lignin is greater than 0 parts by mass and 50 parts by mass or less relative to 100 parts by mass of the total of the lignin and the pitch.

5. A process for producing an asphalt composition according to claim 1 or 2, wherein,

the lignin comprises a dried product of kraft lignin.

6. A process for producing an asphalt composition according to claim 1 or 2, wherein,

the asphalt comprises straight asphalt.

7. A process for producing an asphalt composition according to claim 1 or 2, wherein,

the asphalt comprises asphalt recycled aggregate.

8. A process for producing an asphalt composition according to claim 1 or 2, wherein,

the 1 st mixing step is performed in an open system.

9. A process for producing an asphalt composition according to claim 1 or 2, wherein,

the method includes a holding step of holding the mixture at the predetermined temperature or lower for a predetermined time after the 1 st mixing step.

10. A method for producing an asphalt mixture comprising lignin, asphalt and aggregate, characterized by comprising the steps of,

comprises a raw material mixing step of mixing the lignin, the asphalt, and the aggregate in a state in which the glass transition temperature of the lignin is equal to or lower than a predetermined temperature.

11. The method for producing an asphalt mixture according to claim 10, wherein,

the raw material mixing process comprises the following steps:

a 1 st mixing step of mixing the lignin having a glass transition temperature of the lignin, that is, a predetermined temperature or lower, with the pitch having a predetermined temperature or lower; and

and a 2 nd mixing step of mixing at least the asphalt composition produced in the 1 st mixing step with the aggregate.

12. The method for producing an asphalt mixture according to claim 11, wherein,

in the 2 nd mixing step, the aggregate having the predetermined temperature or lower is mixed with the asphalt composition having the predetermined temperature or lower.

13. The method for producing an asphalt mixture according to claim 10, wherein,

in the raw material mixing step, the lignin and the pitch are mixed so that the lignin is greater than 0 parts by mass and 50 parts by mass or less relative to 100 parts by mass of the total of the lignin and the pitch.

14. The method for producing an asphalt mixture according to claim 10, wherein,

in the raw material mixing step, an aqueous lignin containing the lignin and water is mixed with the aggregate having a temperature equal to or higher than the predetermined temperature so that the lignin is maintained at the predetermined temperature or lower.

15. The method for producing an asphalt mixture according to claim 10, wherein,

in the raw material mixing step, a filler is further mixed,

the filler is mixed in such a manner that the filler is 50 parts by mass or less with respect to 100 parts by mass of the mixture of the lignin and the filler.