阅读说明：本技术 不溶硫喷霜性能的评价方法 (Evaluation method of insoluble sulfur blooming performance ) 是由 高杨 张进 唐志民 于 2020-07-06 设计创作，主要内容包括：本发明提供了一种不溶硫喷霜性能的评价方法。该方法包括：S1,将天然橡胶、填料、硫化促进剂、活性剂、粘合剂、待评价不溶硫、防老剂进行混炼,其重量比100:40～60:0～1.5：5～10:5～10:2～8:0～2,得到未硫化胶样片；S2,将未硫化胶样片在室温下停放,并将不同停放时间下的未硫化胶样片表面的喷霜处的数目、尺寸及喷霜面积占比与喷霜等级进行比对,从而记录不同停放时间下其表面的喷霜等级；表面的喷霜处的数目越多,和/或尺寸越大,和/或喷霜面积占比越高,喷霜等级越高。本发明在模拟混炼工序的前提下,通过多维度评价不同不溶性硫磺的喷霜性能差异,能更准确反映不溶性硫磺的喷霜性能差异,可靠性更高。(The invention provides an evaluation method of insoluble sulfur blooming performance. The method comprises the following steps: s1, mixing natural rubber, a filler, a vulcanization accelerator, an activator, a binder, insoluble sulfur to be evaluated and an anti-aging agent, wherein the weight ratio of the raw materials to the raw materials is 100: 40-60: 0-1.5: 5-10: 2-8: 0-2 to obtain an unvulcanized rubber sample sheet; s2, standing the unvulcanized rubber sample sheet at room temperature, and comparing the number, the size and the frosting area ratio of the frosting positions on the surface of the unvulcanized rubber sample sheet at different standing times with the frosting grade, so as to record the frosting grade of the surface of the unvulcanized rubber sample sheet at different standing times; the greater the number of frosting locations and/or the greater the size of the surface and/or the higher the frosting area fraction, the higher the frosting grade. On the premise of simulating the mixing process, the invention can more accurately reflect the difference of the blooming performance of insoluble sulfur by evaluating the difference of the blooming performance of different insoluble sulfur in multiple dimensions, and has higher reliability.)

1. The method for evaluating the performance of the insoluble sulfur blooming is characterized by comprising the following steps of:

s1, mixing natural rubber, filler, a vulcanization accelerator, an activator, an adhesive, insoluble sulfur to be evaluated and an anti-aging agent to obtain an unvulcanized rubber sample sheet; and the weight ratio of the natural rubber, the filler, the vulcanization accelerator, the activator, the adhesive, the insoluble sulfur to be evaluated and the anti-aging agent is 100 (40-60):

(0～1.5)：(5～10):(5～10):(2～8):(0～2)；

s2, standing the unvulcanized rubber sample sheet at room temperature, and comparing the number, the size and the frosting area ratio of the frosting positions on the surface of the unvulcanized rubber sample sheet at different standing times with the frosting grade, so as to record the frosting grade of the surface of the unvulcanized rubber sample sheet at different standing times; wherein the greater the number of blooming sites on the surface of the uncured rubber-like sheet, and/or the greater the size, and/or the higher the bloom area to volume ratio, the higher the bloom rating.

2. The evaluation method according to claim 1, wherein the unvulcanized rubber sample sheet has a size of 10cm x 12cm, and the blooming grade is 7 grades, each as follows:

level 1: the frosting position is less than or equal to 10 parts, the frosting position is needle-shaped precipitation, the width is less than or equal to 0.1cm, and the area of the frosting position is less than or equal to 0.1 percent of the area of the unvulcanized rubber sample sheet;

and 2, stage: the position of 10 is more than the position of frost spraying and is less than or equal to 30, the position is needle-shaped precipitation, the width is less than or equal to 0.1cm, and the area of the frost spraying position is less than or equal to 0.1 percent of the area of the unvulcanized rubber sample sheet;

and 3, level: the frosting position is more than 30, and is needle-shaped precipitation with the width less than or equal to 0.1cm or at least 1 position is spot-shaped precipitation with the width more than 0.1cm and less than or equal to 1cm, and the area of the frosting position is less than or equal to 1 percent of the area of the unvulcanized rubber sample sheet;

4, level: the frosting part is formed by separating 2-3 mutually independent sheets, the width of the frosting part is more than 1cm and less than or equal to 2cm, and the area of the frosting part is less than or equal to 10% of the area of the unvulcanized rubber sample sheet;

and 5, stage: the frosting position is more than 3, the frosting position is separated out in a mutually independent sheet shape, the width of the frosting position is more than 2cm, the area of the frosting position is more than 10 percent of the area of the unvulcanized rubber sample sheet and is less than or equal to 20 percent of the area of the unvulcanized rubber sample sheet;

and 6, level: the frosting position is more than 3, the frosting position is separated out in a mutually adhered sheet shape, and the area of the frosting position is more than 20 percent of the area of the unvulcanized rubber sample sheet and is less than or equal to 50 percent of the area of the unvulcanized rubber sample sheet;

and 7, stage: the frosted part is separated out in a whole piece, and the area of the frosted part is more than 50 percent of the area of the unvulcanized rubber sample piece.

3. The evaluation method according to claim 1, wherein the step S1 includes:

first-stage mixing: mixing the natural rubber in an internal mixer for 80-100S, then adding the filler, the activator, the adhesive and the anti-aging agent, and mixing to 115-125 ℃; cleaning to 130-140 ℃; cleaning to 360-420S or 140-150 ℃; discharging rubber to obtain master batch;

and (3) second-stage mixing: mixing the master batch in the internal mixer for 50-60S, then adding the insoluble sulfur to be evaluated and the vulcanization accelerator, and mixing for 100-120S; cleaning to 100-110 ℃; and (4) discharging the rubber, and then discharging the rubber from the open mill to obtain the unvulcanized rubber sample sheet with the thickness of 2-3 mm.

4. The evaluation method according to claim 3, wherein in the first mixing step, the initial temperature of the internal mixer is 50 to 60 ℃, and the rotation speed of the rotor is 50 to 70 rpm; in the two-stage mixing step, the initial temperature of the internal mixer is 50-60 ℃, and the rotating speed of a rotor is 50-70 rpm.

5. The evaluation method according to any one of claims 1 to 4, wherein the filler comprises carbon black and white carbon, the vulcanization accelerator is a sulfenamide-based accelerator, the activator is zinc oxide, the adhesive comprises RA-65, resorcinol, and a cobalt salt, and the antioxidant is a p-phenylenediamine-based antioxidant.

6. The method according to any one of claims 1 to 4, wherein in step S2, after the unvulcanized rubber sample sheet is parked at room temperature, the surface of the unvulcanized rubber sample sheet is selected for parking times of 7d, 14d, 21d and 28d, and the corresponding frost level is recorded.

7. The evaluation method according to any one of claims 1 to 4, wherein in step S2, a variation curve of the blooming level of the unvulcanized rubber sample sheet is obtained with the parking time as an abscissa and the blooming level as an ordinate, and the blooming level variation curves of different insoluble sulfur to be evaluated are compared to obtain comparison results of the blooming performance of different insoluble sulfur to be evaluated.

Technical Field

The invention relates to the technical field of performance detection of rubber additives, in particular to an evaluation method of insoluble sulfur blooming performance.

Background

Insoluble sulfur is a linear macromolecular polymer of common sulfur, and has increasingly replaced common sulfur to become a vulcanizing agent of key rubber parts (a belt ply, a tire body, a tire side wall and the like) in a tire. The insoluble sulfur has good compatibility with the olefin elastomer, although the blooming risk of the rubber product can be greatly reduced to a certain extent, the insoluble sulfur can be irreversibly reduced into common sulfur along with the rise of the external storage temperature and the prolongation of the time, so that the surface of the rubber product is blooming and precipitated. Under the existing process conditions, the rubber product is often frosted in the processing process, so that the appearance performance of the product is influenced; for the rubber semi-finished product, the surface frosting of the rubber semi-finished product not only affects the appearance of the final rubber product, but also can cause that the semi-finished product can not meet the production process conditions and the product performance requirements of subsequent reprocessing if the frosting is serious.

The determination of the thermal stability of insoluble sulfur is currently used to indirectly predict the blooming performance of insoluble sulfur in rubber articles. Wherein, the evaluation of the thermal stability of the insoluble sulfur is mainly characterized by heating the insoluble sulfur at a specific temperature and time and measuring the change of the mass percent of the insoluble sulfur before and after heating. There are mainly classified into an oven method, an oil bath method, and a Differential Scanning Calorimeter (DSC) method according to a conductive medium to be heated and a method.

The oven method and the oil bath method adopt a mode of heating first and then cooling, and then part of decomposed sulfur in the sample is washed away; however, there is usually a risk that the soluble sulfur is not completely eluted from the sample, resulting in a deviation in the final measurement result. By analyzing and comparing parameters such as melting point, phase change, enthalpy and the like of the insoluble sulfur, the Differential Scanning Calorimeter (DSC) can relatively comprehensively analyze the thermal stability of the insoluble sulfur. However, the three methods directly evaluate the thermal stability of the insoluble sulfur, and do not consider and simulate the actual performance of the thermal stability of the insoluble sulfur in the actual process of processing, storing and using, thereby easily causing the deviation of the evaluation result and the frosting performance of the final glue product obtained under the actual working condition, reducing the production efficiency and causing serious waste.

In conclusion, a series of detection methods for identifying the degree of insoluble sulfur blooming is lacking at present so as to better guide the actual production.

Disclosure of Invention

The invention mainly aims to provide an evaluation method of insoluble sulfur blooming performance, and aims to solve the problems that deviation exists in the process of identifying the insoluble sulfur blooming performance and actual production is not facilitated to be guided in the prior art.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for evaluating an insoluble sulfur blooming property, comprising the steps of: s1, mixing natural rubber, filler, a vulcanization accelerator, an activator, an adhesive, insoluble sulfur to be evaluated and an anti-aging agent to obtain an unvulcanized rubber sample sheet; and the weight ratio of the natural rubber, the filler, the vulcanization accelerator, the activator, the adhesive, the insoluble sulfur to be evaluated and the anti-aging agent is 100 (40-60) to 0-1.5: (5-10), (2-8), (0-2); s2, standing the unvulcanized rubber sample sheet at room temperature, and comparing the number, the size and the frosting area ratio of the frosting positions on the surface of the unvulcanized rubber sample sheet at different standing times with the frosting grade, so as to record the frosting grade of the surface of the unvulcanized rubber sample sheet at different standing times; wherein the more the number of frosting sites on the surface of the uncured rubber-like sheet, and/or the larger the size, and/or the higher the frosting area ratio, the higher the frosting grade.

Further, the uncured rubber sample piece had a size of 10cm × 12cm, and the blooming rating was 7 grades, which were as follows:

level 1: the frosting position is less than or equal to 10 parts, the frosting position is needle-shaped precipitation, the width is less than or equal to 0.1cm, and the area of the frosting position is less than or equal to 0.1 percent of the area of the unvulcanized rubber sample sheet;

and 2, stage: the position of 10 is less than the position of frost spraying and is less than or equal to 30, the position is needle-shaped precipitation, the width is less than or equal to 0.1cm, and the area of the frost spraying position is less than or equal to 0.1 percent of the area of the unvulcanized rubber sample sheet;

and 3, level: the frosting position is more than 30, and is needle-shaped precipitation with width less than or equal to 0.1cm or at least 1 position is spot-shaped precipitation with width more than 0.1cm and less than or equal to 1cm, and the area of the frosting position is less than or equal to 1% of that of the unvulcanized rubber sample sheet;

4, level: the frosting part is separated from 2-3 mutually independent sheets, the width of the frosting part is more than 1cm and less than or equal to 2cm, and the area of the frosting part is less than or equal to 10% of the area of the unvulcanized rubber sample sheet;

and 5, stage: the frosting position is more than 3, the frosting position is separated out in mutually independent sheets, the width of the frosting position is more than 2cm, the area of the frosting position is more than 10 percent of the area of the unvulcanized rubber sample sheet and is less than or equal to 20 percent of the area of the unvulcanized rubber sample sheet;

and 6, level: the frosting position is more than 3, the frosting position is separated out in a mutually adhered sheet shape, the area of the frosting position is more than 20 percent of the area of the unvulcanized rubber sample sheet and is less than or equal to 50 percent of the area of the unvulcanized rubber sample sheet;

and 7, stage: the frosted part is separated out in a whole piece, and the area of the frosted part is more than 50 percent of the area of the unvulcanized rubber sample piece.

Further, step S1 includes: first-stage mixing: mixing natural rubber in an internal mixer for 80-100S, then adding a filler, an active agent, an adhesive and an anti-aging agent, and mixing to 115-125 ℃; cleaning to 130-140 ℃; cleaning to 360-420S or 140-150 ℃; discharging rubber to obtain master batch; and (3) second-stage mixing: mixing the master batch in an internal mixer for 50-60S, then adding insoluble sulfur and a vulcanization accelerator to be evaluated, and mixing for 100-120S; cleaning to 100-110 ℃; and (4) discharging the rubber, and then discharging the rubber from the open mill to obtain an unvulcanized rubber sample sheet with the thickness of 2-3 mm.

Further, in the first-stage mixing step, the initial temperature of the internal mixer is 50-60 ℃, and the rotating speed of a rotor is 50-70 rpm; in the two-stage mixing step, the initial temperature of the internal mixer is 50-60 ℃, and the rotating speed of a rotor is 50-70 rpm.

Further, the filler comprises carbon black and white carbon black, the vulcanization accelerator is a sulfenamide accelerator, the active agent is zinc oxide, the adhesive comprises RA-65, resorcinol and cobalt salt, and the anti-aging agent is p-phenylenediamine anti-aging agent.

Further, in step S2, after the uncured rubber sample sheet is parked at room temperature, the uncured rubber sample sheet surfaces under parking times of 7d, 14d, 21d and 28d are selected, and the corresponding frost level is recorded.

Further, in step S2, taking the parking time as the abscissa and the blooming level as the ordinate, obtaining the blooming level variation curve of the unvulcanized rubber sample, comparing the blooming level variation curves of different insoluble sulfur to be evaluated, and obtaining the blooming performance comparison results of different insoluble sulfur to be evaluated.

The invention provides an evaluation method of the frosting performance of insoluble sulfur, which simulates the mixing procedure of rubber production and takes a semi-finished rubber material test piece as a frosting performance test sample; and respectively parking the unvulcanized rubber sample wafer for different times in a parking environment at room temperature, comparing the number, the size and the frosting area ratio of the frosting parts on the surface of the unvulcanized rubber sample wafer at different parking times with the frosting grade, and further recording the frosting grade of the surface of the unvulcanized rubber sample wafer at different parking times.

On the premise of simulating the mixing process, the invention can comprehensively evaluate the blooming performance difference of different varieties/batches of insoluble sulfur in the rubber material in a multidimensional way, can more accurately reflect the blooming performance difference of different insoluble sulfur, has higher reliability and can more accurately guide the actual production. Meanwhile, unvulcanized semi-finished rubber is used as a frosting performance detection sample, so that the method is more convenient, and the production time and the working procedures are not greatly occupied. It should be noted that the rating table herein is frosted on the unvulcanized rubber sample, but there are many possibilities of frosting, such as sulfur, anti-aging agent, accelerator, etc. The simulation production process is established under a specific formula system, the dosage relation of natural rubber, filler, vulcanization accelerator, activator, adhesive, insoluble sulfur to be evaluated and anti-aging agent is specifically limited, and the influence of other factors can be avoided to obtain the blooming performance data of the insoluble sulfur in the rubber product.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIGS. 1-7 show photographs of the surface of uncured film with a frost rating of 1 to 7, respectively, for insoluble sulfur in accordance with the present invention; and

FIG. 8 is a graph showing the change in the level of blooming of an unvulcanized film corresponding to four kinds of insoluble sulfur in example 1 of the present invention;

FIG. 9 is a graph showing the change in the level of blooming of an unvulcanized film corresponding to four kinds of insoluble sulfur in example 2 of the present invention;

FIGS. 10 and 11 show surface SEM photographs of an unvulcanized film corresponding to insoluble sulfur in example 1 of the present invention after being left for 28d in a room temperature environment, and sampling points in SEM-EDS analysis are shown in FIG. 11;

FIGS. 12 and 13 show SEM photographs of the surface of an unvulcanized film corresponding to insoluble sulfur in example 2 of the present invention after being left for 28d in a room temperature environment, and the sampling points in the SEM-EDS analysis are shown in FIG. 13;

FIG. 14 is a graph showing the variation of the free sulfur content of each unvulcanized rubber sheet in example 1 of the present invention;

FIG. 15 is a graph showing the change in the surface tackiness of each unvulcanized rubber sheet in example 1 of the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As described in the background section, the prior art has identified deviations in the performance of insoluble sulfur bloom that are not conducive to practical production.

In order to solve the above problems, the present invention provides a method for evaluating an insoluble sulfur blooming property, comprising the steps of: s1, mixing natural rubber, filler, a vulcanization accelerator, an activator, an adhesive, insoluble sulfur to be evaluated and an anti-aging agent to obtain an unvulcanized rubber sample sheet; the weight ratio of the natural rubber, the filler, the vulcanization accelerator, the activator, the adhesive, the insoluble sulfur to be evaluated and the anti-aging agent is 100 (40-60) to 0-1.5: (5-10), (2-8), (0-2); s2, placing the unvulcanized rubber sample sheet at room temperature, and comparing the number, the size and the frosting area ratio of the frosting parts on the surface of the unvulcanized rubber sample sheet at different placing time with the frosting grade, thereby recording the frosting grade of the surface of the unvulcanized rubber sample sheet at different placing time; wherein the more the number of frosting sites on the surface of the uncured rubber-like sheet, and/or the larger the size, and/or the higher the frosting area ratio, the higher the frosting grade.

On the premise of simulating a real mixing process, the method can comprehensively evaluate the blooming performance difference of different varieties/batches of insoluble sulfur in the rubber material in a multidimensional manner, can more accurately reflect the blooming performance difference of different insoluble sulfur, has higher reliability, and can more accurately guide actual production. Meanwhile, unvulcanized semi-finished rubber is used as a frosting performance detection sample, so that the method is more convenient, and the production time and the working procedures are not greatly occupied. It should be noted that the rating table herein is frosted on the unvulcanized rubber sample, but there are many possibilities of frosting, such as sulfur, accelerator, anti-aging agent, etc. The simulation real process is established under a specific formula system, the dosage relation of natural rubber, filler, vulcanization accelerator, activator, adhesive, insoluble sulfur to be evaluated and anti-aging agent is specifically limited, and the influence of other factors can be avoided to obtain the blooming performance data of the insoluble sulfur in the rubber product.

Preferably, the weight ratio of the natural rubber, the filler, the vulcanization accelerator, the activator, the adhesive, the insoluble sulfur to be evaluated and the anti-aging agent is 100:53:1.4:8:9:5: 2.

For the purpose of further improving the evaluation reliability, in a preferred embodiment, the uncured rubber sample sheet has a size of 10cm × 12cm, and the blooming scale is classified into 7 grades, each as follows:

level 1: the frosting position is less than or equal to 10 parts, the frosting position is needle-shaped precipitation, the width is less than or equal to 0.1cm, and the area of the frosting position is less than or equal to 0.1 percent of the area of the unvulcanized rubber sample sheet;

and 2, stage: the position of 10 is less than the position of frost spraying and is less than or equal to 30, the position is needle-shaped precipitation, the width is less than or equal to 0.1cm, and the area of the frost spraying position is less than or equal to 0.1 percent of the area of the unvulcanized rubber sample sheet;

and 3, level: the frosting position is more than 30, and is needle-shaped precipitation with width less than or equal to 0.1cm or at least 1 position is spot-shaped precipitation with width more than 0.1cm and less than or equal to 1cm, and the area of the frosting position is less than or equal to 1% of that of the unvulcanized rubber sample sheet;

4, level: the frosting part is separated from 2-3 mutually independent sheets, the width of the frosting part is more than 1cm and less than or equal to 2cm, and the area of the frosting part is less than or equal to 10% of the area of the unvulcanized rubber sample sheet;

and 5, stage: the frosting position is more than 3, the frosting position is separated out in mutually independent sheets, the width of the frosting position is more than 2cm, the area of the frosting position is more than 10 percent of the area of the unvulcanized rubber sample sheet and is less than or equal to 20 percent of the area of the unvulcanized rubber sample sheet;

and 6, level: the frosting position is more than 3, the frosting position is separated out in a mutually adhered sheet shape, the area of the frosting position is more than 20 percent of the area of the unvulcanized rubber sample sheet and is less than or equal to 50 percent of the area of the unvulcanized rubber sample sheet;

and 7, stage: the frosted part is separated out in a whole piece, and the area of the frosted part is more than 50 percent of the area of the unvulcanized rubber sample piece.

By using the frosting grade, the degree of frosting of the unvulcanized film is divided more differently, so that the change of the frosting performance corresponding to different types of insoluble sulfur is more accurate and clear, and the frosting performance is clearer and better in reliability compared with the quality of the frosting performance of different types of insoluble sulfur. Wherein the photographs of the film surface blooming at the above-mentioned level 1 to level 7 blooming levels are shown in fig. 1 to 7. Based on the blooming grade, the invention can more intuitively and accurately evaluate the blooming performance of the insoluble sulfur in the rubber material in actual production.

The kneading step described above may be performed in a manner as if it were a kneading step for rubber production, but naturally, in order to consider the factors affecting various reagents as much as possible, in a preferred embodiment, step S1 includes: first-stage mixing: mixing natural rubber in an internal mixer for 80-100S, then adding filler, adhesive and anti-aging agent, and mixing to 115-125 ℃; cleaning to 130-140 ℃; cleaning to 360-420S or 140-150 ℃; discharging rubber to obtain master batch; and (3) second-stage mixing: mixing the master batch in an internal mixer for 50-60S, then adding insoluble sulfur and a vulcanization accelerator to be evaluated, and mixing for 100-120S; cleaning to 100-110 ℃; and (4) discharging the rubber, and then discharging the rubber from the open mill to obtain an unvulcanized rubber sample sheet with the thickness of 2.5 mm. More preferably, in the first mixing step, the initial temperature of the internal mixer is 50-60 ℃, and the rotating speed of a rotor is 50-70 rpm; in the two-stage mixing step, the initial temperature of the internal mixer is 50-60 ℃, and the rotating speed of a rotor is 50-70 rpm.

The above-mentioned fillers and other agents may be used in the form of those commonly used in the art, such as: fillers include, but are not limited to, carbon black and white carbon, vulcanization accelerators include, but are not limited to, sulfenamide accelerators, binders include, but are not limited to, one or more of RA-65, cobalt salts, and resorcinol, and antioxidants include, but are not limited to, para-phenylenediamine antioxidants.

In a preferred embodiment, in step S2, after the uncured rubber sample sheet is parked at room temperature, the uncured rubber sample sheet surfaces at parking times of 7d, 14d, 21d and 28d are selected and the corresponding frost level is recorded. The frost spraying grade of the unvulcanized rubber sample sheet is recorded according to the time points, and the frost spraying change can be completely reflected on the basis of saving the detection time.

In a preferred embodiment, in step S2, a variation curve of the blooming level of the uncured rubber sample is obtained with the parking time as the abscissa and the blooming level as the ordinate, and the blooming level variation curves of different insoluble sulfur to be evaluated are compared to obtain different comparison results of the blooming performance of the insoluble sulfur to be evaluated. The frosting performance of different types of insoluble sulfur can be compared and clearly seen by utilizing the frosting grade change curve.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.