CN102205571A - Swelling method for vulcanized rubber - Google Patents

Abstract

The invention relates to diffusion performance of supercritical carbon dioxide in rubber and a swelling method for vulcanized rubber, which are put forward on basis of various excellent characteristics of supercritical fluids and advantages of supercritical carbon dioxide. In the invention, vulcanized rubber is swollen in the presence of supercritical carbon dioxide; according to the characterization of the volume, surface morphology and diffusion coefficient of the swollen vulcanized rubber, it is proved that vulcanized rubber has good swelling performance under the condition of supercritical carbon dioxide.

Description

A kind of swelling method of vulcanized rubber

Technical field

The present invention relates to the swelling method, particularly natural rubber of a kind of vulcanized rubber in supercritical carbon dioxide, butadiene-styrene rubber, the butyl rubber swelling method in supercritical carbon dioxide.

Background technology

In recent years, owing to the consumption of the energy, the pollution of environment, environmental protection and sustainable development are rooted in the hearts of the people.Along with the development of auto industry and rubber industry, waste old produces in a large number.If have a kind of method the waste old environmental protection effectively can be recycled, will make very big contribution for society.

The green technology that the supercritical fluid technique conduct is generally acknowledged in the world: supercritical fluid technique has all obtained extensive use in fields such as food industry, daily-use chemical industry, medical industry, forest product industry, tobacco industry, agricultural chemicals, petrochemical industry, environmental protection, has also caused numerous scholars' concern and attention.Supercritical fluid technique is applied to rubber regeneration, is a brand-new problem.By using particularly supercritical carbon dioxide of supercritical fluid, avoided using organic solvents a large amount of in traditional rubber regeneration, avoided environmental pollution from the source, saved the energy.In addition, utilize supercritical fluid solvent to have the characteristics of adjustability, can change the solvent property of fluid by the temperature and pressure of regulating supercritical fluid easily, thereby control the performance of product.

This paper has studied natural rubber, butadiene-styrene rubber and the butyl rubber swelling method in supercritical carbon dioxide, reclaims waste old for further degrading and prepares.Need desulfurizing agent fully to enter rubber inside during the devulcanization of rubber degraded, the abundant swelling of rubber is the key that desulfurizing agent enters rubber network structure inside, and therefore, the swelling of research vulcanized rubber is significant to the desulfurization degraded of vulcanized rubber.

Summary of the invention

The purpose of this invention is to provide a kind of in supercritical carbon dioxide the method for swelling vulcanized rubber.With vulcanized rubber swelling under the supercritical carbon dioxide condition,, prove that vulcanized rubber under the supercritical carbon dioxide condition, has good swelling behavior by sign to vulcanized rubber volume, surface topography and diffusion coefficient.

The raw material that uses in this programme, medicine and instrument are as follows:

Table 1 raw material and medicine list

Table 2 natural rubber, butadiene-styrene rubber and butyl rubber elastomeric compound prescription

Instrument that uses in the scheme and model specification thereof are:

Servomotor, 123W, Boshan micro machine factory; The artificial intelligence temperature controller, AI-508 type, Xiamen space electric automation Science and Technology Ltd.; Precision balance, JJ1000, the two outstanding fraternal Co., Ltds of the U.S.; Two roller mills, Φ 160 * 320mm, Shanghai rubber manufacturing machinery one factory; The disc type vulcameter, LH-2 type, sulfuration Huan Feng rubber and plastics machine trial (demonstration) plant, tester Beijing; Vulcanizing press, XLB-D350 * 350, Shanghai rubber manufacturing machinery manufactory; The universal material experimental machine, INSTRON, Britain INSTRON company; Differential scanning calorimeter, DSC-2 type, U.S. Perkin-Elmer company.

Concrete grammar and step are as follows:

(1) rubber is mixing

For ease of analyzing, all adopt the prescription of simplifying most when used vulcanized rubber glue is mixing in this experiment, wherein do not contain any filler, antioxidant or wet goods.Natural rubber is undertaken mixing by prescription shown in the table 2, butadiene-styrene rubber is undertaken mixing by prescription shown in the table 3, and butyl rubber is undertaken mixing by prescription shown in the table 4, when reinforced zinc oxide, stearic acid, promoter, sulphur are added sequentially.

(2) test of cure time T90

After placing elastomeric compound more than 6 hours, the about 7g of weighing surveys the cure time T90 of each elastomeric compound with the disc type vulcameter.The caoutchouc vulcanization temperature is 145 ℃, and sulfide stress is 15MPa; The butadiene-styrene rubber curing temperature is 150 ℃, and sulfide stress is 15MPa; The butyl rubber curing temperature is 160 ℃, and sulfide stress is 15MPa.

(3) sulfuration of elastomeric compound

Elastomeric compound is thinly sliced some, every agreement that contracts a film or TV play to an actor or actress 38g puts into 2mm sheet mould, and weighing 9g elastomeric compound is packed in the cylindrical mold, and weighing 7g packs in another cylindrical mold, vulcanizes in the compression molding instrument.Cure time is the T90 of each glue kind correspondence.

(4) the overcritical diffusion of vulcanized rubber

Placed more than one day elastomeric compound sulfuration back, carries out overcritical swelling experiment then.It is some to take from the system vulcanized rubber, claims its quality with assay balance, adopts drainage to measure its volume.After air replaces in reactor with dry ice, with rubber with the some reactors of putting into together of dry ice, progressively be warming up to preset temperature (heating rate be 4 ℃/min), and under design temperature, be incubated certain hour.After insulation finished, the question response still naturally cooled to room temperature and slowly releases wherein carbon dioxide again, obtains swollen rubber.Measure its volume with drainage immediately, then it was left standstill in fume hood 12 hours, thoroughly remove the carbon dioxide of rubber inside, use the assay balance weighing again, every the 1h weighing once, constant until weight.

(5) calculating of carbon dioxide diffusion coefficient

If the swellbility of rubber is ξ (t), soak time is t, and is assumed to isotropic homogeneous phase volumetric expansion, uses radius calculation, and formula is

$\mathrm{\&xi;}\left(t\right)=\frac{V_0+\mathrm{\&Delta;V}\left(t\right)}{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="2.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}={\left(\frac{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="2.png"\; state="\{\{state\}\}">r</figure-callout>}}_0+\mathrm{\&Delta;r}\left(t\right)}{r_0}\right)}^3---\left(1\right)$

Wherein Δ V (t) is the Volume Changes of swollen rubber, V ₀Be 323K, the volume of swollen rubber not under the 0.1MPa, Δ r (t) is the change in radius of swollen rubber, t ₀Be the radius of swollen rubber not.

According to following Theory Thinking, can calculate the diffusion coefficient of carbon dioxide in crosslinked poly-isoprene rubber.The Fick rule of describing the Adsorption law of spherical high polymer liquid towards is expressed as:

$\frac{\mathrm{dC}}{\mathrm{dt}}=\frac{D}{r^2}\frac{d}{\mathrm{dr}}\left(r^2\frac{\mathrm{dC}}{\mathrm{dr}}\right)---\left(2\right)$

Wherein r is the distance to the sample center, and C is the concentration that is dissolved in solvent in the sample, and D is a diffusion coefficient.For radius is the spherical sample of a, and under suitable initial conditions and boundary condition, crank has provided the analysis and solution of formula (3).

$\frac{M_t}{M\&infin;}=1-\frac{6}{{\mathrm{\&pi;}}^2}\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{1}{n^2}\exp \left(\frac{{-\mathrm{Dn}}^2{\mathrm{\&pi;}}^{2}t}{a^2}\right)---\left(3\right)$

The amount of the solvent carbon dioxide when wherein Mt and M ∞ represent time t respectively and reach swelling equilibrium.Integer n represent index adding and.

Enough big and during as t near equilibrium state, be suitable for formula (4) as approaching calculating:

$\frac{M_t}{M\&infin;}=1-\frac{6}{{\mathrm{\&pi;}}^2}\exp \left(\frac{{-\mathrm{D\&pi;}}^2{t}^2}{a^2}\right)---\left(4\right)$

Two supposition are arranged in this experiment: the lengths table that (1) carbon dioxide molecule moves to the center from sample surfaces is shown the start radius a of sample, because the Volume Changes that swelling causes is very small, this hypothesis can not cause the remarkable deviation of calculated value.(2) Volume Changes of Hun Heing be zero and absorption equate with volumetric expansion.On the basis of these two supposition, the amount of solvent carbon dioxide and the pass of swellbility are:

$\frac{M_t}{M\&infin;}=\frac{V_t-V_0}{V_{\&infin;}-{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="2.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}=\frac{\mathrm{\&epsiv;}\left(t\right)-1}{\mathrm{\&epsiv;}(\&infin;)-1}---\left(5\right)$

Wherein ξ (t) (=Vt/V0), the solubility when ξ (∞) is respectively time t and equilibrium state.

(4), (5) formula simultaneous, the pass of swellbility and diffusion coefficient is:

$\ln \left\{\frac{{\mathrm{\&pi;}}^2}{6}\right[1-\frac{\mathrm{\&epsiv;}\left(t\right)-1}{\mathrm{\&epsiv;}(\&infin;)-1}\left]\right\}=\frac{{-\mathrm{D\&pi;}}^{2}t}{a^2}---\left(6\right)$

According to (6) formula

To the time map a straight line, its slope is diffusion coefficient.

Description of drawings

Fig. 1 is the swelling stereoscan photograph (amplify 100 times) of sulfurized natural rubber in supercritical carbon dioxide.

Fig. 2 is crosslinked natural rubber cylinder 1 and cylinder 2 Variation diagram in time.

Fig. 3 is the swelling stereoscan photograph (amplify 100 times) of sulfuration butadiene-styrene rubber in supercritical carbon dioxide.

Fig. 4 is 90 ℃, under the 11MPa, and butadiene-styrene rubber and butyl rubber

Variation diagram in time.

Fig. 5 is the swelling stereoscan photograph (amplify 200 times) of vulcanized butyl rubber in supercritical carbon dioxide.

The specific embodiment

The swelling of embodiment 1 sulfurized natural rubber in supercritical carbon dioxide.

With cylindrical crosslinked natural rubber (d=17.45mm, h=24.30mm, m=5.8056g) in supercritical carbon dioxide under 60 ℃, the condition of 10MPa swelling 60min, 120min, 180min respectively, after swelling finishes, carbon dioxide is discharged, thoroughly remove the carbon dioxide in the sulfurized natural rubber.Because the electron beam in the SEM (abbreviation ESEM) is when sample surfaces scans, have an effect with sample, inspire various signals, as secondary electron, backscattered electron, absorption electronics, auger electrons, feature x ray etc., in bigger sample room, range detector is housed, to detect various signals, make the various signals of reflection sample topography, composition and other physical and chemical performances can both obtain detecting; And have that the depth of field is bigger, the three-dimensional stereo effect of image is good especially, advantage such as distinct third dimension, resolution ratio height are arranged, multiplying power scope is big, the visual field is big and continuous, be fit to very much in this experiment research, so select ESEM method observation glue sample degree of swelling to the inner pattern of swelling glue.

As Fig. 1, Fig. 3, Fig. 5, shown in Figure 6, the vulcanising rubber surface of swelling is very smoothless, does not have hole substantially, in 60 ℃, the supercritical carbon dioxide fluid of 10MPa after the swelling, along with the prolongation swelling hole of swell rubber time increases gradually.At magnification ratio is in 100 times of photos, and it is big and even that the rubber hole behind the swelling 180min becomes; Magnification ratio is in 300 times the photo, as can be seen along with the elongated pore hole dia of swelling time is increasing, before the swelling rubber surface without any bubble and aperture, some uneven apertures appear in rubber surface behind the swelling 60min, it is big that swelling 120min back aperture becomes, and can only see 2 holes in the visual field.Swell to the 180min back aperture and further become big, in the visual field, can only see 1 hole; Can find out clearly that in the photo of 500 times of magnification ratios along with the prolongation of swelling time, hole appears earlier in rubber inside, hole becomes big then, breach appears in the hole inwall, and hole further becomes big when swelling to 180min, and the crackle of hole inwall becomes layered distribution.

By electromicroscopic photograph as can be seen, supercritical carbon dioxide has swelling ability preferably to vulcanized rubber.Along with the prolongation of swelling time, the inner pore quantity of rubber increases gradually, and the aperture increases gradually, and vulcanized rubber finally is swelled into spongy.

Research difformity vulcanized rubber is at the supercritical carbon dioxide diffusion coefficient below.

With cylindrical crosslinked natural rubber (d=17.45mm, h=24.30mm, m=5.8056g, " cylinder 1 ") in supercritical carbon dioxide under 90 ℃, the condition of 11MPa swelling 20min, 40min, 120min, with another cylindrical crosslinked natural rubber (d=28.01mm, h=12.66mm, m=7.8170g, " cylinder 2 ") also with above-mentioned condition under swelling 20min, 40min, 120min, volume sees Table 3 before and after the swelling.

Volume Changes before and after the diffusion of table 3 natural rubber

As can be seen from the above table, when cylindrical rubber in supercritical carbon dioxide under 90 ℃, the condition of 11MPa during swelling 120min, volume sweell(ing) is 59.3ml to the limit.Utilize the diffusion coefficient formula, when calculating different swelling time

To the t mapping, carry out linear fit, as Fig. 2.Trying to achieve straight slope is-9.686 * 10 ^-4, and then try to achieve diffusion coefficient.Show in the table 3 that under 90 ℃, the condition of 11MPa during swelling 120min, volume also is swelling to the limit to the cylindrical rubber of another shape, is 70ml in supercritical carbon dioxide.Utilize the diffusion coefficient formula, when calculating different swelling time

To the t mapping, carry out linear fit, as Fig. 3, trying to achieve straight slope is-8.0609 * 10 ^-4, and then try to achieve diffusion coefficient.

The two shape difference is bigger, but the slope after the mapping is respectively-9.686 * 10 ^-4,-8.0609 * 10 ^-4, difference is very little, illustrates that shape is very little to the diffusion coefficient influence of rubber, can ignore.Cylindrical volume is similar to as the spheroid volume, calculates radius of sphericity, trying to achieve diffusion coefficient at last is 5.2 * 10 ^-8m ²/ s.

Volume Changes before and after the diffusion of table 4 different temperatures natural rubber

According to Masaaki Kojima, at 323K, under the condition of 10MPa, recording diffusion coefficient is 1.1 * 10 ^-9m ²/ s.Illustrate that the rising temperature, pressure can improve diffusion coefficient.Shown in the table 4, the swelling situation of each shape cylinder when temperature is respectively 90 ℃ and 95 ℃.Cylinder 1 in the time of 90 ℃ after the swelling volume be 53.5ml, in the time of 95 ℃ after the swelling volume be 63ml; Cylinder 2 in the time of 90 ℃ after the swelling volume be 65ml, swelling volume is 80.5ml in the time of 95 ℃.As seen the temperature that raises has improved the swelling ability of supercritical carbon dioxide to rubber.

The swelling of embodiment 2 butadiene-styrene rubber in supercritical carbon dioxide.

Butadiene-styrene rubber in supercritical carbon dioxide, in 90 ℃, is carried out diffusion reaction under the condition of 11MPa, Volume Changes sees Table 5 before and after the swelling.

Volume Changes before and after the diffusion of table 5 butadiene-styrene rubber

After reaching supercriticality as shown in Table 5, carbon dioxide well is diffused into butadiene-styrene rubber inside.Along with the increase in reaction time, the volume of diffusion back butadiene-styrene rubber increases gradually, and promptly carbon dioxide is diffused into the interior amount of butadiene-styrene rubber increases in time and increase.Behind reaction 120min, diffusion reaches capacity, and volumetric expansion is to 32.5ml.

Fig. 3 is the swelling stereoscan photograph (amplify 100 times) of sulfuration butadiene-styrene rubber in supercritical carbon dioxide.From photo, can clearly find out, the vulcanising rubber surface of swelling is very smoothless, substantially there is not hole, in 90 ℃, the supercritical carbon dioxide fluid of 11MPa after the swelling, along with the prolongation swelling hole of swell rubber time increases gradually, the rubber hole behind the swelling 120min becomes many and is uniformly dispersed, as seen, supercritical carbon dioxide has swelling ability preferably to sulfuration butadiene-styrene rubber, and along with the inner pore quantity of the prolongation rubber of swelling time increases gradually, the aperture increases gradually.

Calculate according to carbon dioxide diffusion formula And to time t mapping, as shown in Figure 4.

Linear substantially with t, appoint and to get at 2 to ask its slope be-1.21495 * 10 ^-5, get final product to such an extent that diffusion coefficient is 8.2 * 10 ^-10m ²/ s.

The swelling of embodiment 3 butyl rubbers in supercritical carbon dioxide

90 ℃, under the 11MPa condition, butyl rubber spreads front and back volume such as table 6 through different time in supercritical carbon dioxide.

Volume before and after the diffusion of table 6 butyl rubber

As shown in Table 6, prolongation along with diffusion time, the cylinder volume of butyl rubber increases gradually, be that the amount that carbon dioxide diffuses in the rubber matrix gets more and more, behind diffusion reaction 120min, the volumetric expansion of butyl rubber tends towards stability afterwards substantially to 60ml, and the carbon dioxide that enter in the rubber matrix this moment is 51ml.

Fig. 5 and the vulcanized butyl rubber swelling stereoscan photograph (amplifying 200 times) in supercritical carbon dioxide.From photo, can clearly find out, the vulcanising rubber surface of swelling is very smoothless, substantially there is not hole, in 90 ℃, the supercritical carbon dioxide fluid of 11MPa after the swelling, along with the prolongation swelling hole of swell rubber time increases gradually, in the visual field, have only a bigger hole during swelling 40min, and three big holes are arranged in the swelling 120min rearward vision.By electromicroscopic photograph as can be seen, supercritical carbon dioxide has swelling ability preferably to vulcanized butyl rubber.Along with the inner pore quantity of the prolongation rubber of swelling time increases gradually, the aperture increases gradually.

Calculate according to carbon dioxide diffusion formula

And to the t mapping, as shown in Figure 4, the two is linear substantially.At 90 ℃, under the 11MPa condition, its slope is-6.60411 * 10 ^-5, calculating diffusion coefficient is 4.46 * 10 ^-9m ²/ s.

Compare natural rubber, the diffusion coefficient of butadiene-styrene rubber butyl rubber finds that the diffusion coefficient maximum of natural rubber is 5.2 * 10 ^-8m ²/ s, the diffusion coefficient minimum of butadiene-styrene rubber is 8.2 * 10 ^-10m ²/ s, the diffusion coefficient that different rubber are described is different, this structure with rubber inside is relevant.

In addition, one skilled in the art should appreciate that under the situation that does not deviate from spirit of the present invention described herein or essential characteristic, can realize the present invention with other concrete forms, and the present invention is not limited to specific embodiments as described herein.Therefore, disclosed embodiment all is considered to illustrate rather than limit in all respects at present.The scope of application of the present invention is by additional claim explanation, rather than by the specification explanation of front, and all changes of being made in meaning and scope and their equivalence change and all think and be included in wherein.

Claims (3)

1. the swelling method of a vulcanized rubber, it is characterized in that vulcanized rubber swelling under the supercritical carbon dioxide condition, by sign, prove that vulcanized rubber under the supercritical carbon dioxide condition, has good swelling behavior to vulcanized rubber volume, surface topography and diffusion coefficient.

2. method according to claim 1, the concrete steps of its realization are as follows:

(1) natural rubber or butadiene-styrene rubber or butyl rubber are carried out mixing sulfuration by setting prescription, cure time is the T90 of each glue kind correspondence;

(2) after the mixing of rubber sulfuration, it is some to take from the system vulcanized rubber, claim its quality with assay balance, adopt drainage to measure its volume, after air replaces in reactor with dry ice, with rubber with the some reactors of putting into together of dry ice, progressively be warming up to predetermined temperature, wherein heating rate is 4 ℃/min, and the insulation certain hour obtains swollen rubber under design temperature, measure its volume with drainage immediately, in fume hood, left standstill then 12 hours, and thoroughly removed the carbon dioxide of rubber inside, use the assay balance weighing again, every the 1h weighing once, constant until weight;

(3), calculate the calculating of carbon dioxide diffusion coefficient according to the gained data.

3. according to the method for claim 2, it is characterized in that: rubber temperature retention time in reactor is 60-80min.

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