Pulverulent mixtures containing low-emission nitrile rubbers

Abstract

Pulverulent mixtures containing at least one nitrite rubber and at least one release agent, which are characterized by a particular average particle diameter, are provided. These mixtures have particularly low emissions and are outstandingly suitable for producing materials and components for indoor applications.

Claims

1. A pulverulent mixture comprising: (1) at least one nitrile rubber which has repeating units of at least one ,-unsaturated nitrite monomer and at least one conjugated diene monomer and has an emission ratio E according to the formula (I) of less than or equal to $\begin{array}{cc}E=\frac{\left[\mathrm{volatile}\mathrm{constituents}\right]}{\left[\mathrm{Mooney}\mathrm{viscosity}\right]}\frac{\left[\mathrm{Nitrile}\mathrm{content}\right]}{100}& \left(I\right)\end{array}$ 0.25 mg/(kg*Mooney units), where [volatile constituents] is the concentration of volatile constituents in mg/kg of nitrite rubber determined by means of a TDS-GC/MS examination in accordance with the VDA 278 recommendation (09.2002 version) in the range from 28.4 minutes to 34.0 minutes, [Mooney viscosity] is the Mooney viscosity ML 1+4 at 100 C. of the nitrite rubber determined in accordance with ASTM D 1646 and reported in Mooney units, and [nitrite content] is the dimensionless content of the ,-unsaturated nitrite in the nitrite rubber, determined in % by weight by the Kjeldahl method in accordance with DIN 53 625, and (0) one or more release agents, wherein particles of the pulverulent mixture have an average particle diameter Da of 0.01 to 4 mm.

2. The pulverulent mixture according to claim 1, wherein the release agent(s) is/are selected from the group consisting of silica, calcium carbonate, silicate, PVC and fatty acid salts.

3. A process producing a pulverulent mixture according to claim 1, the process comprising contacting the nitrite rubber component with the one or more release agents.

4. The process for producing a pulverulent mixture according to claim 3, wherein the nitrile rubber component is produced by a process that comprises either a milling step or else a spray drying step, during the course of which contacting with the release agent(s) occurs in each case.

5. Composites comprising: (A) at least one pulverulent mixture according to the invention according to claim 1; and (B) one or more thermoplastic polymers.

6. The composites according to claim 5, wherein the thermoplastic polymers are selected from the group consisting of polyvinyl chloride, polyurethanes, polyamides, epoxy resins, phenolic resins, polypropylene, polyethylene, polyethylene-vinyl acetate and polystyrene.

7. The composites according to claim 6, wherein the thermoplastic polymers are selected from the group consisting of polyvinyl chloride, polyurethanes and polyamides.

8. The composites according to claim 5, wherein the components (A) and (B) are used in a weight ratio of (1-99):(99-1), preferably (10-60):(90-40), based on the sum of the components (A) and (B).

9. A process for producing the composites according to claim 5, the process comprising mixing the two components (A) and (B) with one another.

10. A method for producing articles of manufacture, the method comprising producing the articles the composites according to claim 5, wherein the articles of manufacture comprise components for use in automobile interiors.

11. Components based on composites according to claim 5.

12. The pulverulent mixture according to claim 1, wherein the particles have an average particle diameter Da of 0.2 mm to 1.5 mm.

13. The pulverulent mixture according to claim 1, wherein the particles have an average particle diameter Da of 0.08 mm to 0.12 mm.

14. The pulverulent mixture according to claim 1, wherein the nitrite rubber has an emission ratio E according to the general formula (I) of less than or equal to 0.20 mg/(kg*Mooney units).

Description

EXAMPLES

I. Analysis

(1) Acrylonitrile Content:

(2) The nitrogen content for determining the acrylonitrile content was determined in the nitrile rubbers according to the invention by the Kjeldahl method in accordance with DIN 53 625.

(3) Mooney Determination:

(4) The determination of the Mooney viscosity (ML 1+4 @ 100 C.) was carried out at 100 C. in accordance with ASTM D 1646.

(5) Particle Size Determination:

(6) The particle size of the pulverulent mixture was determined granulometrically. For this purpose, 100 g of the pulverulent mixture were weighed into a sieve having a mesh opening of 2.0 mm. Further sieves having mesh openings of 1.4 mm, 1.0 mm, 0.8 mm, 0.6 mm and 0.3 mm were placed underneath this sieve. The assembled sieves are clamped on a vibratory sieving machine (AS 200 control g from Retsch) and vibrated at an amplitude of 2.00 mm for a period of 30 minutes. The individual sieves were then weighed and the average particle size D.sub.n was calculated according to the following formula:
D.sub.a=(X.sub.iD.sub.i)/100
where
D.sub.a is the average particle diameter in mm,
X.sub.i is the percentage of the total particle mass in g retained on the respective sieve and
D.sub.i is the average mesh opening of the respective sieve n and n+1 in mm.

(7) Furthermore,
D.sub.i=(D.sub.n+D.sub.(n+1))/2
where
D.sub.n is the mesh diameter of the sieve n in mm and
D.sub.(n+1) is the mesh diameter of the sieve n+1 in mm.

(8) The volatile organic constituents of the nitrile rubbers were quantified in accordance with VBA 278 (2011 version) by means of thermodesorption gas chromatography (TDS-GC/MS).

II. Preparation of NBR Polymers A and B

(9) As basis for producing the examples according to the invention and the comparative examples, two NBR polymers A and B, as indicated in Table 1, were prepared and used.

(10) TABLE-US-00001 TABLE I Preparation of the NBR polymers A and B (Amounts indicated each in parts by weight based on 100 parts of total monomers (butadiene and acrylonitrile)) B Nitrile rubber A Comparison Butadiene (total) 64.15 64.15 Acrylonitrile (total/increment).sup.1) 35.85/9 35.85/9 phr phr Total amount of water 200 200 Oleic acid.sup.2) 1.5 1.5 Resin acid.sup.3) 0.6 0.6 AOS.sup.4) 0.4 0.4 Sulphole 120/t-DDM.sup.5) 0.31/0.13 (total/increment) Solphole 90.sup.6) (total/increment) 0.31/0.13 Trigonox NT 50.sup.7) 0.031 0.031 Premix FeSO.sub.4.sup.8) 0.027 0.027 Diethylhydroxylamine 0.14 0.14 Vulkanox BKF.sup.9) 0.3 0.3 pH.sup.10) 11.0 1.0 11.0 1.0 Polymerization temperature [ C.] 10.0 0.5 10.0 0.5 Polymerization conversion [%] 78 78 .sup.1)The addition of the increment was carried out at a monomer conversion of 36% .sup.2)Oleic acid CAS number 67701-06-08 .sup.3)Resin acid CAS number 61790-51-0 .sup.4)AOS sodium -olefin sulphonate .sup.5)Sulphole 120 t-DDM (tertiary dodecyl mercaptan) Chevron Philips Chemicals .sup.6)Sulphole 90 (tertiary nonyl mercaptan) Chevron Philips Chemicals .sup.7)p-menthane hydroperoxide (Trigonox NT 50 from Akzo-Degussa) .sup.8)containing the reducing agent Rongalit C (sodium salt of a sulphinic acid derivative) and the Fe(II) salt in the amounts indicated above. .sup.9)2-[(2-hydroxy-5-methyl-3-tert-butyl-phenyl)methyl]-4-methyl-6-tert-butyl-phenol Lanxess Deutschland GmbH .sup.10)measured at the beginning of the polymerization

(11) The preparation of the nitrile rubbers A and B was carried out continuously in a cascade of stirred vessels. After introduction of the monomers, the soap AOS and the chain transfer agent (in the amounts indicated in Table 1 based on 100 parts of total monomer) and bringing the contents of the reactor to temperature, the reaction was started by introduction of aqueous solutions of iron(II) salts (in the form of the premix solutions) and of para-menthane hydroperoxide (Trigonox NT50). The reaction mixture was pumped through the cascade of stirred vessels and when the desired conversion had been reached, the polymerization was terminated by addition of an aqueous solution of diethylhydroxylamine in the last reactor. Unreacted monomers and other volatile constituents were removed by stripping under reduced pressure.

(12) Before coagulation, the NBR latex was in each case admixed with a 50% strength dispersion of Vulkanox BKF (0.3% by mass of Vulkanox BKF based on NBR solid). Coagulation and washing were subsequently carried out and the crumbs obtained were dried.

III. Production of Pulverulent Mixtures of NBR A or B and a Release Agent (Examples 1 and 2)

(13) The pulverulent mixtures of NBR and a release agent were prepared on the basis of the NBR polymers A and B, as follows. The amount of NBR crumbs (in g) indicated was intimately mixed with the indicated amount in each case of release agent calcium carbonate (in g). This mixture was gradually introduced into an ultracentrifugal mill ZM 200 (Retsch) to which the cyclone was attached. The mill was equipped with an annular sieve having an average mesh opening of 1 mm and was operated at a speed of 18 000 rpm. The powder was continuously removed from the milling chamber and collected by means of the cyclone during the course of the milling operation.

(14) TABLE-US-00002 TABLE 2 Production of the pulverulent mixtures (Example 1 and 2) 2 Pulverulent 1 (comparison) mixture (g) (g) NBR A 90 NBR B 90 Calcium carbonate 10 10

IV. Production of Pulverulent Mixtures of NBR, a Release Agent and a Thermoplastic (Examples 3 and 4 (Dry Blend))

(15) The dry blends were produced by mixing the amounts (in g) indicated in Table 3 in a planetary mixer. The mixer was maintained at 100 C. The pulverulent PVC was introduced together with the stabilizer Mark CZ 97** into the mixing apparatus, and the NBR powder mixtures were added after a mixing time of 5 minutes. After mixing for a further 10 minutes, the dry blend is taken from the mixing apparatus and the material is allowed to cool to room temperature before further processing

(16) TABLE-US-00003 TABLE 3 Production of mixtures of NBR, a release agent and a thermoplastic (Examples 3 and 4) 4 3 (comparison) Mixtures (g) (g) Pulverulent mixture 100 from Example 1 Pulverulent mixture 100 from Example 2 Vinnolit S 4170* 300 300 Mark CZ 97** 9 9 *Polyvinyl chloride, pulverulent, from Vinnolit GmbH & Co. KG **Calcium/zinc stabilizer from Galata Chemicals

V. Extruded Mixtures of NBR, a Release Agent and a Thermoplastic (Composites) (Examples 5 and 6)

(17) The composites were produced by means of a laboratory extruder Plasti-Corder Lab Station from Brabender. The single-screw extruder had four different heating zones. The temperatures of the individual zones were set to 155 C., 160 C., 165 C. and 170 C. at the commencement of introduction of the sample. The screw was operated at a speed of 100 rpm. A slit-shaped die having a width of 2.5 mm served as tool. The pulverulent Examples 3 and 4 (dry blends) were fed to the extruder. After introduction for about 30 s, a homogeneous extrudate (composite) was obtained.

VI. Summary of the Analysis for all Examples

(18) The analytical results on the starting NBR A and B samples and also the pulverulent mixture with the release agent, the mixture with PVC as thermoplastic and the corresponding composites are shown in Table 4 below.

(19) It can clearly be seen that the example according to the invention based on an NBR having an emission coefficient of 0.041 mg/(kg*Mooney units), which is thus below 0.25 mg/(kg*Mooney units), correspondingly also leads to composites which are low-emission materials and can thus be used for critical indoor applications without problems and restrictions.

(20) TABLE-US-00004 TABLE 4 Analysis of the nitrile rubbers A and B and also Examples 1-6 (n.d. means not determined) Nitrile rubber/pulverulent mixture/mixture/- B 2 4 6 composite A Comparison 1 Comparison 3 Comparison 5 Comparison ACN total (%) 32.3 33.7 n.d. n.d. n.d. n.d. n.d. n.d. Mooney viscosity 55 48 n.d. n.d. n.d. n.d. n.d. n.d. (ML1 + 4 @ 100 C.) (MU) Average particle size n.d. n.d. 0.62 0.62 n.d. n.d. n.d. n.d. D.sub.4 (mm) total VOC (mg/kg).sup.1 88 129 57 109 45 43 15 12 Emission coefficient.sup.2 0.041 0.412 0.039 0.333 0.015 0.066 0.003 0.012 E (mg/kg) .sup.1Total VOC was determined in accordance with VDA 278. .sup.2$E=\frac{\left[\mathrm{volatile}\mathrm{constituents}\right]}{\left[\mathrm{Mooney}\mathrm{viscosity}\right]}\frac{\left[\mathrm{Nitrile}\mathrm{content}\right]}{100}\left(I\right)$
where [volatile constituents] is the concentration of volatile constituents in mg/kg of nitrile rubber determined by means of a TDS-GC/MS examination in accordance with the VDA 278 recommendation (09.2002 version) in the range from 28.4 minutes to 34.0 minutes, [Mooney viscosity] is the Mooney viscosity ML 1+4 at 100 C. of the nitrile rubber determined in accordance with ASTM D 1646 and reported in Mooney units, and [nitrile content] is the content of ,-unsaturated nitrile in the nitrile rubber in % by weight, determined by the Kjeldahl method in accordance with DIN 53 625.