JP6935681B2 - How to evaluate the dispersion of silica aggregates - Google Patents

Description

The present invention relates to a method for evaluating the dispersion of silica aggregates in a silica-blended rubber.

Rubber compositions used for pneumatic tires and the like are required to improve various performances (fuel efficiency performance, wear resistance performance, wet grip performance, etc.), and as a method for that purpose, improvement of filler dispersion, etc. is being studied. ing.

For the evaluation of filler dispersion, a method of examining the "Pain effect" by taking the strain dependence of the storage elastic modulus G'in the dynamic viscoelasticity measurement is often used. The "pain effect" evaluates ΔG'(= G'(maximum value) -G'(minimum value)), which is the difference between the maximum value and the minimum value of G'in the measurement range. It can be said that the proportion of large filler aggregates is small and the dispersed state is good.
In addition, a method of quantifying the variance by image analysis by TEM is also used.

However, in the "Pain effect", the dispersion of the filler from the nanometer scale, which is the primary particle size of the filler, to the centimeter scale, which is the size of the rubber, has an effect, and the dispersion of the filler aggregates in the entire rubber can be quantitatively evaluated. However, there is a problem that it is not possible to quantitatively evaluate only the dispersion of silica aggregates on the scale of several tens of nanometers as a spatial scale.
Further, the evaluation by TEM has a problem in statistical accuracy because the measurement field of view is narrow.

An object of the present invention is to solve the above problems and to provide a method capable of accurately and quantitatively evaluating only the dispersion of silica aggregates in a silica-blended rubber.

In the present invention, in the region of q represented by the following (Equation 1), the scattering intensity curve I _dry (q) obtained by irradiating the silica-blended rubber with X-rays or neutron rays and the silica-blended rubber swollen with a solvent are blended. _{The ratio I dry} (q) of the _{scattering intensity curve I swell} (q) obtained by irradiating the rubber with X-rays or neutrons ^{to the I corr} _swell (q) obtained by correcting the scattering intensity S with the swelling degree S as shown in the following equation. q) / I ^corr _swell (q) relates to a method for evaluating the dispersion of silica aggregates in a silica-blended rubber.
I ^corr _swell (q) = I _swell (q) × swelling degree S / 100
Swelling degree S = ((volume of silica-blended rubber + volume of solvent) / volume of silica-blended rubber) × 100

The region of q preferably contains 0.001 <q <0.05 Å ^-1.

According to the present invention, the scattering intensity curve I _dry (q) obtained by irradiating the silica-blended rubber with X-rays or neutrons and the silica-blended rubber swollen with a solvent are irradiated with X-rays or neutrons. From the ratio I _dry (q) / I ^corr _swell ^{(q) with the I corr} _swell (q) obtained by correcting the obtained scattering intensity curve I _swell (q) with the degree of swelling, silica in the silica-blended rubber Since this is a method for evaluating the dispersion of aggregates, only the dispersion of silica aggregates in the silica-blended rubber can be evaluated accurately and quantitatively.

Is an X-ray scattering of the vulcanized rubber composition 1 obtained by measuring ^{_{I dry (q) / I corr}} swell (q).

_{In the method of the present invention, the scattering intensity curve I dry} (q) obtained by irradiating the silica-blended rubber with X-rays or neutrons in the region of q represented by the following (formula 1) and swelling with a solvent. The ratio I of _{the scattering intensity curve I swell} (q) obtained by irradiating the silica-blended rubber with X-rays or neutrons ^{to the I corr} _swell (q) obtained by correcting the swelling degree S as shown in the following equation. The dispersion of silica aggregates in the silica-blended rubber is evaluated from _dry (q) / I ^color _{swell (q).}
I ^corr _swell (q) = I _swell (q) × swelling degree S / 100
Swelling degree S = ((volume of silica-blended rubber + volume of solvent) / volume of silica-blended rubber) × 100

The scattering intensity curve I (q) is the product of the filler aggregation information P (q) and the filler aggregation dispersion information S (q). When swell silica compounded rubber, dispersed information S (q) ≒ 1 next to the filler ^{agglomeration,} _{I corr swell} (q) can be approximated with filler aggregation information _{^{P (q) (I corr swell}} (q) ≈ P (q)). Therefore, from I _dry (q) / I ^corr _swell (q), information on the dispersion of filler aggregation S (q), that is, information on the dispersion of silica aggregates in the silica-blended rubber can be obtained, and in the silica-blended rubber. Only the dispersion of silica aggregates in the above can be quantitatively evaluated.

In the present invention, the silica aggregate means a silica primary aggregate having a size of several tens of nm to several μm.

First, in the present invention, the silica-blended rubber is irradiated with X-rays or neutrons _{to obtain a scattering intensity curve I dry} (q).

The silica-blended rubber is a crosslinked rubber in which silica is blended and rubber components such as natural rubber and styrene butadiene rubber are crosslinked with a vulcanizing agent generally used in the rubber industry such as sulfur and a vulcanization accelerator. , Not particularly limited, other compounding agents widely used in the rubber industry (reinforcing agents such as carbon black other than silica, silane coupling agents, zinc oxide, stearic acid, various antioxidants, oils, waxes, crosslinks. Agents, etc.) may be included. Such a silica-blended rubber can be produced by using a known kneading method or the like.

As a method of irradiating a silica-blended rubber with X-rays to _{obtain a scattering intensity curve I dry} (q), a small-angle X-ray scattering method (scattering angle: usually 10 degrees or less) (hereinafter, SAXS (Small-Angle X-ray Scattering)) ) Measurement) can be preferably adopted. In the small-angle X-ray scattering method, structural information of a substance can be obtained by measuring the X-rays scattered by irradiating the substance with X-rays and having a small scattering angle, such as a microphase-separated structure of a crosslinked rubber. , Non-uniform structure at the level of several nanometers can be analyzed.

Further, as a method of irradiating the silica-blended rubber with neutron rays to _{obtain a scattering intensity curve I dry} (q), a small-angle neutron scattering method (scattering angle: usually 10 degrees or less) (hereinafter, SANS (Small-Angle Neutron Scattering)). (Also referred to as measurement) can be preferably adopted. In small-angle neutron scattering, the structure information of a substance can be obtained by measuring the neutron rays scattered by irradiating the substance with a small scattering angle, and several nanometers such as the microphase-separated structure of crosslinked rubber. Non-uniform structure at the level can be analyzed.

As the X-ray brightness and the number of photons in the SAXS measurement, the neutron flux intensity of the neutron beam in the SANS measurement, the measuring method, the measuring device and the like, those described in JP-A-2014-102210 can be preferably adopted. Although the SANS measurement is superior in terms of contrast, it is preferable to use the SAXS measurement in that it is versatile and the effects of the present invention can be obtained satisfactorily.

The SAXS and SANS measurements are carried out in the region of q represented by the following (Equation 1).

The region of q preferably contains 0.001 <q <0.05 Å ^-1. This makes it possible to evaluate the dispersion of silica aggregates.

The X-rays scattered in the SAXS measurement are detected by the X-ray detection device, and an image is generated by an image processing device or the like using the X-ray detection data from the X-ray detection device.

Examples of the X-ray detector include a two-dimensional detector (X-ray film, nuclear dry plate, X-ray imaging tube, X-ray fluorescence enhancer tube, X-ray image intensifier, X-ray imaging plate, X-ray CCD. , X-ray amorphous body, etc.), line sensor one-dimensional detector can be used. The X-ray detector may be appropriately selected depending on the type and state of the polymer material to be analyzed.

As the image processing device, a device capable of generating a normal X-ray scattered image based on the X-ray detection data by the X-ray detection device can be appropriately used.

SANS measurement can be performed by the same principle as SAXS measurement. Scattered neutron rays are detected by a neutron beam detection device, and an image is generated by an image processing device or the like using the neutron beam detection data from the neutron beam detection device. Will be done. Here, as described above, as the neutron beam detection device, a known two-dimensional detector or one-dimensional detector can be used, and as the image processing device, a known neutron beam scattering image can be generated, and if appropriately selected. good.

Then, according to the invention, X-ray or solvent silica compounded rubber swollen with the (scattering intensity curve I _{dry (q)} silica compounded rubber same silica compounded rubber and obtained silica compounded rubber swollen with solvent) _{The scattering intensity curve I swell} (q) obtained by irradiating with neutron rays is corrected by the swelling degree S as shown in the following equation ^{to obtain I corr} _swell (q). In the present invention _{, I dry} (q) may be obtained ^{after obtaining I corr} _swell (q).
I ^corr _swell (q) = I _swell (q) × swelling degree S / 100
Swelling degree S = ((volume of silica-blended rubber + volume of solvent) / volume of silica-blended rubber) × 100

The method for swelling the silica-blended rubber with a solvent is not particularly limited as long as it can swell the silica-blended rubber, and a known method can be used, and a method using a solvent such as toluene can be preferably used. The conditions for swelling are not particularly limited as long as the silica-blended rubber can be swelled uniformly, but the silica-blended rubber and an arbitrary amount of solvent can coexist in the closed container to uniformly swell the entire silica-blended rubber. preferable. To uniformly swell the silica-blended rubber means that the solvent used for swelling is evenly distributed in the silica-blended rubber, and the solvent is unevenly present in the silica-blended rubber, so that the silica-blended rubber is in a warped state. It refers to the state in which it does not become.

Generally, when the silica-blended rubber is swollen with a solvent or the like, the silica-blended rubber is warped. In the state where such warpage occurs, the solvent and the like are not evenly distributed in the silica-blended rubber, and the silica-blended rubber and the solvent are allowed to coexist for preferably 6 hours or more, more preferably 12 hours or more. A silica-blended rubber can be prepared in which the solvent and the like are evenly distributed in the silica-blended rubber, the warp is eliminated, and the entire silica-blended rubber is uniformly swollen.

The degree of swelling S in the swollen silica-blended rubber is defined as ((volume of silica-blended rubber) + (volume of compound used for swelling)) / (volume of silica-blended rubber) × 100 (%). The volume of the compound (solvent) used means the volume of the compound (solvent) stored in the rubber by the silica-blended rubber.

As the swelled silica-blended rubber, for example, when a silica-blended rubber having ^{a volume of 100 mm 3 is used, a rubber having a swelling degree of 200% to which 100 mm 3} of toluene is added or a swelling degree to which 200 mm ³ of toluene is added is used. 300% of the rubber can be used.

The swelling degree S may be appropriately set according to the blending of the silica-blended rubber and the like so as to obtain the effect of the present invention. For example, 200% or more is preferable, and 300% or more is more preferable.

_{As a method for obtaining the scattering intensity curve I swell} (q) by irradiating the swollen silica-blended rubber with X-rays or neutrons, the same method as the above-mentioned method for obtaining the scattering intensity curve I _dry (q) can be applied. ..

The obtained I _swell (q) is corrected by the swelling degree S as shown in the following formula ^{to obtain I corr} _swell (q). Thereby, the difference in the degree of swelling between the samples can be corrected.
I ^corr _swell (q) = I _swell (q) × swelling degree S / 100

Finally, in the present invention, from the ratio I _drive (q) / I ^color _{silica (q) of the obtained I drive} (q) and I ^color _silica (q), preferably from the wave vector q dependence of the ratio. , Evaluate the dispersion of silica aggregates in silica-blended rubber.

As described above, since the ratio I _dry (q) / I ^corr _swell (q) contains only the information on the dispersion of the filler aggregation, the dispersion of only the silica aggregate in the silica-blended rubber can be quantitatively evaluated. .. Thereby, for example, the dispersion of the filler aggregate in the entire rubber due to the "pain effect" can be investigated in more detail, and it can be used for controlling the silica dispersion focusing on the silica aggregate.

The present invention will be specifically described based on examples, but the present invention is not limited thereto.

Hereinafter, various chemicals used in Examples and Comparative Examples will be collectively described.
(Reagent used)
Toluene: BR 150B manufactured by Kanto Chemical Co., Ltd .: BR 150B manufactured by Ube Industries, Ltd.
Silica: Nipsil VN3 manufactured by Tosoh Silica Co., Ltd.
Stearic acid: silane coupling agent manufactured by NOF Corporation 1: 3-octanoylthiopropyltriethoxysilanesilane coupling agent manufactured by General Electric Silicones 2: NXT-Z45 manufactured by Momentive.
Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. 1: Noxeller NS (N-tert-butyl-2-benzothiazyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Production of Vulcanized Rubber Compositions 1 and 2)
According to the compounding contents shown in Table 1, the compounding ingredients excluding sulfur and the vulcanization accelerator are kneaded with a 1.7 liter sealed vanbury mixer for 3 minutes or more, and when the temperature reaches 140 ° C., the compounded rubber is discharged and the base is used. It was made of kneaded rubber. The base kneaded rubber, sulfur and a vulcanization accelerator were kneaded with an open roll, and the obtained kneaded product was vulcanized to obtain vulcanized rubber compositions 1 and 2.

<Comparative example: Pain effect>
With respect to the obtained vulcanized rubber composition, G'with a strain of 0.5 and 5% was measured under the conditions of 100 ° C. and 1 Hz using an RPA2000 type testing machine manufactured by Alpha Technologies, and the following formula was used. ΔG'was calculated.
ΔG'= G'(0.5% strain) -G'(5% strain)

<Example>
(Sample preparation)
The obtained vulcanized rubber composition was sliced to a thickness of 0.5 mm to prepare a non-swelling rubber sample.
Toluene was added to a 0.5 mm thick non-swelling rubber sample so that the swelling degree S defined by the following formula was 300%, and the sample was allowed to stand in a closed container for 12 hours or more to swell and swell. It was used as a rubber sample.
Swelling degree S (%) = ((volume of vulcanized rubber composition + volume of toluene) / volume of vulcanized rubber composition) × 100

(measurement)
The SAXS experiment was carried out with the non-swelling rubber sample as it was and with the swollen rubber sample placed in a closed cell. The equipment and measurement conditions used in SAXS are shown below.

[SAXS device]
SAXS measuring device attached to beamline BL08B2 of SPring-8, a large-scale radiation facility owned by the High Brightness Photon Science Research Center [Measurement conditions]
X-ray brightness (8 keV): 9.5 x 10 ¹⁵ photos / s / mrad ² / mm ² / 0.1% bw
Number of X-ray photons: 10 ⁹ to ¹⁰ photos / s
Distance from sample to detector: 2.58m
[Detector]
High-speed two-dimensional X-ray detector PILATUS 100K (manufactured by Vectors)

A non-scattering intensity curve obtained from the rubber specimen swelling _{^I dry} (q), _I ^corr corrected scattering intensity curve _{I swell} obtained from rubber samples swell the (q) in degree of swelling S as shown in Equation since the _{swell (q),} was determined _{^{I dry (q) / I corr}} swell (q).
I ^corr _swell (q) = I _swell (q) × swelling degree S / 100

The results of Examples and Comparative Examples are shown in Table 2 and FIG.

From Table 2 and FIG. 1, in the vulcanized rubber compositions 1 and 2 in which the dispersion of silica aggregates was different because different silane coupling agents were used, no difference was observed in the pain effect of the comparative example, but in Examples. It was found that the difference can be detected by the method of the present application. Therefore, it was found that only the silica aggregate dispersion in the silica-blended rubber can be evaluated accurately and quantitatively by the method of the present application.

Claims (2)

_{In the region of q represented by the following (Equation 1), the scattering intensity curve I dry} (q) obtained by irradiating the silica-blended rubber with X-rays or neutrons, and the X-rays on the silica-blended rubber swollen with a solvent. Alternatively, the scattering intensity curve I _swell (q) obtained by irradiating a neutron beam is corrected by the swelling degree S as shown in the following equation, and the ratio ^{to the I corr} _{swell (q) obtained is I dry} (q) / I. A method for evaluating the dispersion of silica aggregates in a silica-blended rubber from ^corr _{swell (q).}
I ^corr _swell (q) = I _swell (q) × swelling degree S / 100
Swelling degree S = ((volume of silica-blended rubber + volume of solvent) / volume of silica-blended rubber) × 100

The method for evaluating the dispersion of a silica aggregate according to claim ¹ , wherein the region of q contains 0.001 <q <0.05 Å -1.

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