CALCIUM CARBONATE COMPRISING COMPOSITION FOR ELASTOMERIC FILM PREPARATION

Abstract

The present invention concerns a composition for the preparation of an elastomeric film. Furthermore, the present invention concerns the use of such a composition for the preparation of an elastomeric film, a method for preparing an elastomeric film and an elastomeric film produced by the inventive method.

Claims

1. A composition for the preparation of an elastomeric film comprising: a) at least one latex, b) at least one curing system, and c) at least one filler composition, wherein the filler composition consists of a mixture of i) a first calcium carbonate-comprising material having a calcium carbonate content of at least 90 wt.-%, based on the total weight of the first calcium carbonate-comprising material, and having a weight median particle size d.sub.50 value in the range from 0.6 m to 2 m and a steepness factor of at least 40; and ii) a second calcium carbonate-comprising material having a calcium carbonate content of at least 90 wt.-%, based on the total weight of the second calcium carbonate-comprising material, and having a weight median particle size d.sub.50 value in the range from 0.3 m to 1 m and a steepness factor of at least 20, wherein the weight median particle size d.sub.50 value of the first and the second calcium carbonate-comprising material differs by 0.1 m to 1.1 m.

2. The composition according to claim 1, wherein the at least one latex of a) is a natural latex, a synthetic latex or a mixture thereof.

3. The composition according to claim 1, wherein at least one stabilizer is present in the composition.

4. The composition according to claim 1, wherein the first and/or the second calcium carbonate-comprising material is/are selected from the group consisting of ground calcium carbonate.

5. The composition according to claim 1, wherein the first calcium carbonate-comprising material has i) a weight median particle size d.sub.50 value in the range from 0.6 m to 2 m, and/or ii) a top cut (d.sub.98) of 20 m, and/or iii) a residue on a 45 m sieve of 1 wt.-% based on the total dry weight of the first calcium carbonate-comprising material, and/or iv) the amount of particles <2m is 80 wt.-%, based on the total dry weight of the first calcium carbonate-comprising material, and/or v) a residual total moisture content of from 0.01 wt.-% to 1.5 wt.-%, based on the total dry weight of the first calcium carbonate-comprising material, and/or vi) a calcium carbonate content of at least 93 wt.-%, based on the total dry weight of the first calcium carbonate-comprising material, and/or vii) a HCl insoluble content of 10 wt.-% based on the total dry weight of the first calcium carbonate-comprising material, and/or viii) a steepness factor of at least 45.

6. The composition according to claim 1, wherein the first calcium carbonate-comprising material is used in form of a powder.

7. The composition according to claim 1, wherein the second calcium carbonate-comprising material has i) a weight median particle size d.sub.50 value in the range from 0.4 m to 0.9 m, and/or ii) a top cut (d.sub.98) of 20 m, and/or iii) a residue on a 45 m sieve of 1 wt.-% based on the total dry weight of the second calcium carbonate-comprising material, and/or iv) the amount of particles <1m is 70 wt.-%, based on the total dry weight of the second calcium carbonate-comprising material, and/or v) a calcium carbonate content of at least 93 wt.-%, based on the total dry weight of the second calcium carbonate-comprising material, and/or vi) a HCl insoluble content of 10 wt.-% based on the total dry weight of the second calcium carbonate-comprising material, and/or vii) a steepness factor of at least 22.

8. The composition according to claim 1, wherein the second calcium carbonate-comprising material is used in form of an aqueous suspension.

9. The composition according to claim 1, wherein the dry weight ratio of the first to the second calcium carbonate-comprising material is from 5:95 to 30:70.

10. The composition according to claim 1, wherein the composition has a pH value from 7 to 13.

11. The composition claim 1, wherein the composition has a viscosity in the range of 50 to 200 mPa.Math.s.

12. The composition according to claim 1, wherein the curing system is present in the composition in an amount of at least 1 phr, based on the at least one latex.

13. The composition according to claim 1, wherein the at least one filler composition is present in the composition in an amount of at least 1 phr, based on the at least one latex.

14. The composition according to claim 1, wherein the composition is suitable for the preparation of an elastomeric film.

15. A method for preparing an elastomeric film comprising the steps of A) providing a coagulant solution B) providing at least one composition for the preparation of an elastomeric film according to claim 1, C) providing at least one former, D) dipping the former of step C) in the solution of step A), E) drying or partially drying the coagulant-dipped former of step D), F) dipping the coagulant-coated former of step E) into the composition of step B) to produce a layer of the composition of step B) on the coagulant-coated former, G) drying the layer of the composition formed on the coagulant-coated former, H) optionally dipping the former obtained in step G) into the composition of step B) to produce a further layer of the composition of step B) and drying said further layer, I) optionally repeating step H), J) leaching the former obtained in step G) and/or step H) and/or step I) in an aqueous solution, K) heating the former obtained in step J) to produce the total elastomeric film, and L) stripping the total elastomeric film from the former.

16. The method according to claim 15, wherein the total solid content of the composition of step B) is between 5 wt.-% to 50 wt.-%, based on the total weight of the composition of step B).

17. The method according to claim 15, wherein the at least one coagulant solution is an aqueous composition comprising at least one coagulant selected from the group consisting of calcium nitrate, calcium chloride, magnesium nitrate, acetic acid, formic acid, sodium silicofluoride and mixtures thereof.

18. The method according to claim 15, wherein the at least one coagulant solution comprises at least one releasing agent selected from the group consisting of a non-mineral material, a polymer of polyacrylate, polyurethane, starch, and a metal soap, and a mineral material.

19. The method according to claim 15, wherein step J) is performed in water.

20. The method according to claim 15, comprising the additional step of cooling the elastomeric film-coated former of step K) to temperatures from 15 C. to 30 C.

21. The method according to claim 20, comprising an additional coating step after step K) and before step L) of treating with a releasing agent selected from the group consisting of a non-mineral material, a polymer of polyacrylate, polyurethane, starch, and a metal soap, and a mineral material.

22. An elastomeric film produced by the method of claim 15.

23. The elastomeric film according to claim 22, wherein the filler in the elastomeric film is present in an amount of 1 wt.-% to 40 wt.-%, based on the total weight of the elastomeric film.

24. The elastomeric film according to claim 22, wherein the film is in the form of a glove, a balloon, a condom, a probe cover, a dental dam, a finger cot, a catheter or a film.

25. The elastomeric film according to claim 22, wherein the average thickness of the total elastomeric film is between 0.01 and 6.0 mm.

26. The elastomeric film according to claim 25, wherein the film is in the form of a glove, wherein the glove has a higher mechanical strength compared to a glove that has been prepared the same way, wherein said glove that has been prepared the same way comprises i) a first calcium carbonate-comprising material having a calcium carbonate content of at least 90 wt.-%, based on the total weight of the first calcium carbonate-comprising material and having a weight median particle size d.sub.50 value in the range from 0.6 m to 2 m and a steepness factor of at least 40 or ii) a second calcium carbonate-comprising material having a calcium carbonate content of at least 90 wt.-%, based on the total weight of the second calcium carbonate-comprising material and having a weight median particle size d.sub.50 value in the range from 0.3 m to 1 m and a steepness factor of at least 20.

Description

EXAMPLES

[0329] 1 Measurement Methods and Materials

[0330] In the following, measurement methods and materials implemented in the examples are described.

[0331] Particle Size

[0332] The particle distribution of the untreated ground calcium carbonate-comprising filler material was measured using a Sedigraph 5120 from the company Micromeritics, USA. The method and the instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement was carried out in an aqueous solution comprising 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and supersonics.

[0333] Specific Surface Area (BET)

[0334] The specific surface area was measured using nitrogen and the BET method according to ISO 9277.

[0335] Elongation at Break

[0336] Unaged and aged films were tested according to procedures specified in DIN EN 455-2:2009 Physical properties.

[0337] Mechanical Properties of Films

[0338] The tensile properties (ultimate tensile strength) and the modulus of the unaged films and aged films at 100 C. for 22 hours were determined using an Instron 5565 testing machine according to the ASTM D412 with a crosshead speed of 500 mm/min. The test was conducted under room temperature (251 C.).

[0339] Dumbbell test specimen were stamp-cut with Die D as specified in ASTM D412.

[0340] Viscosity

[0341] The viscosity measured is a Brookfield viscosity measured using Brookfield RVTDV-II instrumentation at 20 rpm, and selecting the spindle such that the % mode value lies between 20 and 80.

[0342] 2 Materials

[0343] SYNTHOMER 6330.sup.T: An aqueous, colloidal dispersion of carboxylated butadiene-acrylonitrile copolymer with a medium acrylonitrile level. The dispersion contains an emulsifier system and is stabilized with an antioxidant.

[0344] OCTOCURE 462.sup.T: Zinc Oxide 60 wt.-% aqueous dispersion, based on the total weight of the dispersion. The zinc oxide is based on French process zinc oxide produced via a direction oxidation of zinc ingot. The dispersion is commercially available from Tiarco Chemical and used without further treatment.

[0345] OCTOCURE 456.sup.T: Sulfur in aqueous dispersion, ball-milled to a uniform small particle size, 70 wt.-% total solids, based on the total weight of the dispersion. The dispersion is commercially available from Tiarco Chemical and used without further treatment.

[0346] OCTOCURE 573.sup.T: Zinc Oxide 60 wt.-% dispersion, based on the total weight of the dispersion, which can be readily incorporated directly into latex emulsion compounds. The dispersion is commercially available from Tiarco Chemical and used without further treatment.

[0347] OCTOCURE ZDE-50 .sup.T: Zinc diethyldithiocarbamate 50 wt.-% aqueous dispersion, based on the total weight of the dispersion. The dispersion is commercially available from Tiarco Chemical and used without further treatment

[0348] Filler composition 1 (comparative): Natural ground calcium carbonate in a slurry form, commercially available from Omya International AG, Switzerland (d.sub.50=0.6 m; d.sub.98=3 m; content of particles <1 m=80 wt.-%, based on the total dry weight of the natural ground calcium carbonate; solids content=50 wt.-%, based on the total weight of the aqueous suspension; density of slurry=1500 Kg/m.sup.3; viscosity=200 mPas; steepness factor 26).

[0349] Filler composition 2 (comparative): Natural ground calcium carbonate in a powder form, commercially available from Omya International AG, Switzerland (d.sub.50: 0.9 m; d.sub.98=4 m; content of particles <2 m=90 wt.-%, based on the total dry weight of the natural ground calcium carbonate; steepness factor 66).

[0350] Filler composition 3 (inventive): Mixture of filler composition 1 (90 wt.% based on the total weight of the filler composition 3, calculated from the dry weight of the natural ground calcium carbonate in filler compositions 1 and 2) and filler composition 2 (10 wt.% based on the total weight of the filler composition 3).

[0351] Preparation of the Compositions

[0352] 1) Preparation of the Nitrile Latex Compounding Formulation

[0353] NBR latex (Acrylonitrile Butadiene Rubber) branded Synthomer 6330 was compounded in the lab following the below formulation (Table 1). More precisely, all the components listed in Table 1 were mixed in a beaker except the filler composition X. The mixture was continuously stirred for 24 hours. Then 5 phr of the filler composition X was added to the compounded NBR latex.

TABLE-US-00001 TABLE 1 Nitrile latex compounding formulation Ingredients phr NBR (Synthomer 6330) 100 KOH 1.0 ZnO (Octocure 573) 1.2 Sulfur (Octocure 456) 0.8 Zinc diethyldithiocarbamate 0.8 (ZDEC) (Octocure ZDE) Filler composition X 5.0

[0354] 2) Preparation of the Coagulant Solution

[0355] The coagulant solution comprised 20 wt.% of calcium nitrate.

[0356] 3) Preparation of Unaged Films

[0357] The former (unglazed porcelain plates) were first dipped into the coagulant solution and afterwards, the coagulant-dipped formers were dried at 60-70 C. for 20 seconds.

[0358] After the drying step, the formers were then dipped into the freshly prepared nitrile latex compounding formulation as described above and afterwards partially dried further at 60-70 C. for 20 seconds.

[0359] The formed latex films were then subjected to a leaching step; i.e. subjected to a warm water (50-55 C.) immersion for 2 minutes.

[0360] The films underwent a heating step, wherein the latex films were heated in an oven at 120 C. for 20 minutes to form the desired elastomeric nitrile films. The formers were then removed from the oven and cooled to room temperature, before being powdered with USP grade corn starch. Then the films were stripped off from the former to obtain the unaged films. The mechanical properties of the cured unaged films were then tested.

[0361] 4) Preparation of Aged Films

[0362] The cured unaged films above were further aged in an oven at 100 C. for 22 hours to obtain aged films.

[0363] Results

[0364] 1) Unaged

TABLE-US-00002 TABLE 2 Mechanical properties of the unaged films obtained using various filler compositions Modulus (MPa) UTS EB Unaged 0 100 300 500 (MPa) (%) 1) Control (without filler) 0 1.851 3.579 9.277 26.031 614.8 2) Filler Composition 1 0 2.522 5.607 17.613 32.226 573.1 3) Filler Composition 2 0 2.138 4.096 9.383 27.675 628.2 5) Filler Composition 3 0 2.36 4.85 13.85 33.654 645.2 UTS = Ultimate Tensile Strength EB = Elongation at Break

[0365] As it can be seen from Table 2 the inventive composition comprising the filler composition 3 shows a synergetic effect on the ultimate tensile strength and elongation at break compared to the comparative filler composition 1 and 2 taken alone. The ultimate tensile strength and the elongation at break of the unaged films produced with the composition 3 according to the present invention are considerably improved and superior compared to the filler compositions 1 and 2 taken alone.

[0366] 2) Aged

TABLE-US-00003 TABLE 3 Mechanical properties of the aged films obtained using various filler compositions Aged Modulus (MPa) UTS EB (oxidation) 0 100 300 500 (MPa) (%) 1) Control (without filler) 0 2.417 5.692 21.35 26.804 526 2) Filler Composition 1 0 2.861 7.264 25.994 31.287 521.1 3) Filler Composition 2 0 2.954 6.814 18.292 27.659 529 5) Filler Composition 3 0 2.726 6.31 19.54 32.581 615.3 UTS = Ultimate Tensile Strength EB = Elongation at Break

[0367] As it can be seen from Table 3, the inventive composition comprising the filler composition 3 shows a synergetic effect on the ultimate tensile strength and elongation at break compared to the filler composition 1 and 2 taken alone. The ultimate tensile strength and the elongation at break of the aged films produced with the composition 3 according to the present invention are considerably improved and superior compare to the filler compositions 1 and 2 taken alone.