KR100235128B1 - Elastomeric film products with improved chemical resistance - Google Patents

Abstract

The present invention provides a preventive condom, surgical glove, comprising a molded film consisting essentially of a) a copolymer of acrylonitrile and butadiene or isoprene and b) a cured mixture of styrene-butadiene copolymer of high styrene content. It provides a latex film product with enhanced chemical resistance, such as medical examination gloves.

Description

[Name of invention]

Elastomeric film with enhanced chemical resistance

Detailed description of the invention

The present invention relates to elastomeric film products such as contraceptive condoms and surgical gloves made from certain acrylonitrile containing synthetic latex.

[Background of invention]

Commercially available condoms have been made of natural rubber (NR) latex for the last 30 years. Natural rubber latex can be easily mixed with aqueous dispersions of hardeners such as sulfur, zinc oxide, preservatives, etc. and is stable, so it is an excellent material for latex dipping processes commonly used to manufacture products such as condoms, medical gloves, etc. to be. In addition, when immersion shaping formers are immersed in latex, an actual immersion process is simple since a film matching the male surface is formed. In addition, heat is rapidly evaporated to form a natural rubber film having a uniform thickness and integrity.

In order to minimize the number of pores in the condom, it is common practice to secondary immerse the dried male film in latex. After vulcanization by heating at 100 ° C. for about 1 hour, the natural rubber condoms show good tensile strength, extensibility and good tear resistance. However, since natural rubber is an unsaturated hydrocarbon elastomer, resistance to heat, light, oxygen, ozone, and bacteria is poor. In addition, trace metals such as copper facilitate the decomposition of natural rubber.

Natural rubber is also easily swelled, weakened, and degraded by contact with chemical emulsions, in particular by hydrocarbon oils and solvents. It is well known that natural rubber condoms are very weak when lubricated by some components of feminine hygiene products and therapeutic creams, in addition to mineral oil, petroleum jelly and vegetable oils. Often, condoms tear or decompose upon contact with these materials, making them unusable.

Laboratory gloves and surgical gloves are generally made of natural rubber latex. Although such gloves are sufficiently strong and durable for the handling of medical equipment, physical contact, and the like, they are also easily weakened by contact with laboratory chemicals, hygiene products, dental compounds, and body fluids. Thus, the production of gloves, condoms and other elastomeric film products from synthetic latexes that provide good resistance to chemicals, lubricants and the like is highly encouraged in terms of commercial and stability.

It is also necessary to lubricate the condom for the majority of users. Since there is no natural rubber compatible with user-available lubricants, most condoms are prelubricated at the factory using special silicone oils not available to the public. Due to these low viscosity oil properties, application methods and packaging methods, condoms are applied completely as lubricants on their own inside and outside. Lubrication of the inner surface of the condom may promote undesired slipping and deformation, thereby increasing the frequency of occurrence of breakage or waste of the condom induced by deformation even during normal use.

The concept of sectional lubrication using chemically selected condoms such as petroleum jelly and baby oil can be introduced into chemically resistant condoms. This can significantly reduce the rate of condom failure by reducing the actual deformation by the condom lubricated only in the cross section. Deformation can be reduced by improving the skin adhesion of the condom by avoiding lubrication of the inner surface of the condom while maintaining the outer lubrication layer that would be required in a realistic environment.

Very recently, the potential for severe allergic reactions caused by contact with natural rubber latex products has been found. Protein residues in latex products are responsible for this allergic reaction. Such allergic reactions may cause contact urticaria or systemic hypersensitivity. In other words, a person with allergic symptoms may experience pruritus, rash, wheezing or more severe symptoms when using natural rubber latex condoms or gloves. For these reasons and other technical and economic factors, there is a desire to expand the use of non-allergic synthetic latex materials such as the materials described herein in the manufacturing industry.

The present invention provides an elastomeric film product such as a condom with improved chemical resistance. Due to this improved chemical resistance, it is possible to use a lubrication system that can safely apply only the outer surface of the condom. Lubricant is applied to the outer surface of the condom through a solvent and the coating is dried before rolling. This prevents the lubrication system from transferring from outside to inside. Many such lubricants must be applied through a non-aqueous solvent system, so such lubricants can be used only for chemically resistant condoms.

In addition, the user can use a non-toxic petroleum based lubricant in his home to meet the need for better lubrication effect. Moreover, the condoms provided in accordance with the present invention significantly reduce the risk of breakage of the condoms, which can be caused by the interaction of the condoms and excipients, allowing the female to continue to receive vaginal therapy by drug treatment.

[Simple Summary of Invention]

The present invention relates to a molded film consisting essentially of a purifying mixture of a copolymer of acrylonitrile with butadiene or isoprene (a) and a high styrene styrene-butadiene copolymer (b) containing at least about 50% by weight of polymerized styrene. Highstyrene styrene-butadiene copolymer (b) in the film is used in a ratio of about 1 to about 15% by weight based on the weight of the copolymer (a) of acrylonitrile and butadiene or isoprene). Latex film products such as contraceptive condoms, surgical gloves, medical examination gloves, etc., having improved chemical resistance, are provided. In a preferred embodiment, both copolymers are carboxylated to improve the “green strength” of the uncured molded film, which facilitates the production of the inventive product.

[Prior art]

US Pat. No. 4,955,392 describes a contraceptive condom made of a combination of a low modulus polyolefin, such as low density polyethylene, and a thermoplastic elastomer, which may in particular be a nitrile rubber.

Many publications report chemical resistance of immersed latex gloves made of nitrile rubber (mostly reinforced latex, some made from very thick films). See, e.g., Silkowski et al. AVAILABLE GLOVE MATERIALS BY TWO PENTACHLOROPHENOL FORMULATIONS, Am. Ind. Hyg. Assoc. J. 45 (8), 501-504 (1984)].

Detailed description of the invention

The synthetic acrylonitrile-based copolymer used in the present invention is a latex composed of acrylonitrile and butadiene or isoprene. The acrylonitrile-based copolymer is mixed with high styrene styrene-butadiene latex. Preferably, these two latexes are carboxylated to improve the “untreated strength” of the uncured film during processing.

Products, such as condoms and gloves, made from the latex of the present invention in accordance with procedures similar to the known commercially available latex forming processes, have good physical properties and good resistance to petroleum lubricants, petrochemical solvents and industrial chemicals.

Synthetic acrylonitrile-based copolymer latex used in the present invention is a commercial product class. Therefore, its properties and preparation methods are known. Preferred acrylonitrile-based copolymer latex contains acrylonitrile in an amount sufficient to impart the necessary chemical resistance required for special applications. For example, smaller amounts of acrylonitrile are used to produce condoms, because chemicals such as hydrocarbon lubricants or auxiliaries found in formulations administered in the vagina to which the condom is exposed (as described above) This is because the chemical acts very mildly against the condoms of the present invention, even if the chemicals are strong enough to have adverse effects on the natural rubber condoms. Thus, the proportion of acrylonitrile in the latex copolymer is usually in a low state, ie from about 15 to about 40 weight percent based on the latex copolymer, with the remainder being isoprene or butadiene. Since medical gloves may be exposed to more powerful chemicals, higher amounts of acrylonitrile are generally preferred. Thus, when the latex film product of the present invention is a surgical glove, the amount of acrylonitrile in the latex copolymer may be about 20 to about 55% by weight based on the latex copolymer, with the remainder being isoprene or butadiene. In some cases, it is desirable to carboxylate the latex copolymer to impart improved raw strength to the molded uncured latex product. When the latex copolymer is carboxylated, third monomers such as acrylic acid, methacrylic acid and the like are generally copolymerized with acrylonitrile and butadiene and / or isoprene. The degree of carboxylation is generally about 1 to about 10 weight percent. In this paragraph,% means% based on monomer units containing carboxylic acid functional groups.

High styrene styrene-butadiene latex or known materials used in the present invention. Therefore, its properties and preparation methods are known. The high styrene-butadiene latex used has a polymerized styrene content of at least 50% by weight, for example up to about 90% by weight and preferably from about 75 to 85% by weight and the residual amount of latex is butadiene. The latex can also be carboxylated to the extent mentioned for the acrylonitrile containing latex above to enhance the raw strength of the molded, uncured latex film product.

High styrene styrene-butadiene latex is used in an amount sufficient to improve the tear strength of the latex film product. Generally, high styrene styrene-butadiene latex is used at a ratio of about 1 to about 25 parts by weight, preferably about 2 to about 15 parts by weight per 100 parts of acrylonitrile-based latex, where the ratio is on a solid basis.

The following experiment illustrates the method used to mold the latex film product of the present invention.

[Experiment]

The following description relates to the manufacture of a contraceptive condom in accordance with the present invention. When the present invention is used to produce other types of latex film products, known modifications to this method can be used. For example, in the manufacture of surgical and medical gloves, only one latex drip process is generally used, which is calcium nitrate, calcium chloride, chloride in a suitable solvent mixed with a coagulant (e.g., a surfactant). Immersed in a polyvalent metal salt such as zinc). Coagulants are provided to aggregate the latex particles in a uniform manner. After latex dipping, if a coagulant is used, a coagulant step is generally used to remove coagulant salts prior to the drying / curing step.

Latex formulations are prepared in laboratory organic instruments and stored in sealed containers. The vessel is rolled continuously to ensure good dispersion and to allow the formulation to be completed for a suitable time, usually 48 to 72 hours before immersion.

The components used are listed below. The formulations of the examples are shown in their dry content.

In order to obtain good wet film flow, uniform thickness and good inner layer adhesion, thickeners such as sodium polyacrylate are added to try hard to obtain the proper viscosity of the master batch.

Film dipping is performed with a 5-station laboratory dipping machine. Male dips for aluminum dip are in the form of condoms with an approximate diameter of 3.5 cm.

The male is kept stationary and the vessel containing the latex is raised so that the male is immersed in the latex. At the beginning of the immersion sequence, containers containing various latex mixtures are placed in trays mounted directly below the males. The tray is hydraulically lifted at 40 cm / min, so that the male is almost completely immersed in the latex.

In the second step, the tray is lowered at a rate of 20 cm / minute until the male is completely out of the latex. Immediately thereafter, the male is rotated at a speed of 10 rpm around the vertical axis to move to the horizontal position. During rotation, irradiate with a Boekamp 1500 W quartz heater (model 1001) at a distance of 20 cm from the male. Subsequently, the immersion and drying sequence are repeated to obtain a double layer consisting of a continuous rubber film. It is standard practice to perform a double dipping process to ensure that no pores are present in the manufacture of condoms.

The males are removed from the immersion and left in the curing oven at 100 ° C. for 55 minutes. After curing, the males are removed from the oven and allowed to cool for 15 minutes. Talc the film and simply pull it off.

In commercial scale operations, the process performed is expected to be very similar to the methods used industrially to produce latex film products molded from natural rubber latex. However, there are some differences. In commercial scale operations, natural rubber latex can be “pre-vulcanized” to partially cure the natural rubber latex polymer to shorten the curing time and / or lower the curing temperature required for the molded product, ie natural rubber The latex can be placed in a tank at a temperature of about 70 ° C. for about 5 hours. It is not known whether such pre-vulcanization treatments can be performed on the molded latex film products of the present invention. Thus, the curing conditions of the molded article will be longer or higher or both than those generally used for commercial scale production of natural rubber latex film articles. For example, the temperature used in the curing tunnel section of a conventional dipping machine may be set to 10 to 15 ℃ higher than the temperature used in the production of natural rubber products. In addition, as done in commercial scale operations, the condom must be washed and tumble dried at 90 ° C. for about 30 minutes in a rotary dryer to complete the curing process.

[material]

Acrylonitrile-isoprene (“A-I”) latex is commercially available from BASF Canada Inc. Acrylonitrile-isoprene Ilatex is based on copolymerization of 33% acrylonitrile and 67% isoprene in emulsion at low temperatures using a redox catalyst system. Following polymerization, it is concentrated by evaporation to increase the solids content and stabilize by addition of a biocide. The internal properties of the material are as follows:

2. BUTOFAN Latex-Buttophan LN426C is a carboxylated acrylonitrile-butadiene (“A-B”) latex available from BASF Inc. This is a 40% solids carboxylated acrylonitrile-butadiene copolymer emulsion containing about 45% polymerized acrylonitrile, viscosity low at 20 cps, pH 10.0. Its carboxylation degree is about 5%.

3. High Styrene Styrene-Butadiene Latex-Two high styrene styrene-butadiene latexes are used in the experiment. It contains about 80% polymerized styrene and is a high carboxyl carboxylated styrene-butadiene copolymer with a solids content of 50%, a pH of 9.0 and about 2% carboxylated:

(i) Latex DL816 commercially available from The Dow Chemical Co.

(ii) Styronal ND846 available from BASF Incorporated.

4. A 10% aqueous solution of KOH-reagent grade potassium hydroxide.

5. Potassium oleate-20% aqueous solution of potassium oleate.

6. Potassium laurate-20% potassium laurate solution prepared from concentrate.

7. ZDC-Zinc diethyl dithiocarbamate. This is a cure accelerator provided as 50% aqueous emulsion.

8. TMTD-Tetramethyl Thiuram Disulfide is a cure accelerator provided as a 50% aqueous emulsion.

9. ZnO—Zinc Oxide is a cure activator that is provided as a 50% aqueous emulsion.

10. Sulfur is provided as a 65% aqueous dispersion. It acts as a primary vulcanizing agent for natural rubber.

11.Wingstay L is an antioxidant produced exclusively by Goodyear Chemical Co. and is a 50% aqueous dispersion by General Latex and Chemicals Co. Commercially available.

12. Thiourea is a pure chemical compound.

13. Polyresin 5544—Sodium polyacrylate solution commercially available from BASF Incorporated. Used as a thickener.

14. ICI is a proprietary commercial bactericidal compound prepared from the reaction of proxel CRL-4-methyl phenol with dicyclopentadiene and isobutylene.

[Physical Characteristic Test]

After curing the film, it is peeled off from the male using talc to minimize tack and self-adhesion. Test samples are cut from rubber films using steel dies and hydraulic systems. Physical testing is performed at room temperature with minimal aging time.

[Tear Strength Test]

Tear strength is assessed using an Instron Series IX automated materials testing system and ASTM method D624-54. The specimen is cut using a reduced size (but identical geometrical) version of die 'C' (90 ° notch, 6 cm long). The thickness (T) of each specimen at the notch is measured with a digital micrometer. The gauge length or grip length GL is 70 mm and the Instron crosshead speed is 500 mm / min. The tear strength (N / cm) is calculated from the formula F / T, where the maximum load (F) is measured by Instron. Elongation at break is calculated by the formula (D / GL) × 100 where the break displacement (D) is measured by an Instron system.

[Tear Strength Test Using Dumbbell-shaped Die]

The tear strength of the specimens is evaluated using an Instron Series IX automated material test system. ASTM method D412-83 is performed using a small version of dumbbell die 'C' (6 cm long). The gauge length (GL) used is 12 mm and the Instron crosshead speed is 100 mm / min. The thickness of each specimen is measured using a digital micrometer and the average of three readings in the narrow area is recorded. Tear strength (MPa) is determined from equation F / A, where maximum load (F) is measured by Instron and area (A) is calculated using the width of the narrow area of the sample and their respective thicknesses. . The breaking strain (%) is calculated by the formula (D / GL) × 100 (where the breaking displacement (D) is measured by an Instron system).

Discussion of Examples and Test Results

(i) Preparation of Condoms from Buttophan Acrylonitrile-Butadiene Latex

Table 1 shows dry weight formulations of three representative butopan latex compounds. These are similar compounds, and compounds B and C differ from compound A in that high styrene styrene-butadiene latex is added.

Condoms are prepared by the double immersion technique as described above and tested for physical properties. The average test results are shown in Table 2.

Cured double immersion films of butanepan latex provide very high tensile strengths of 37.8 MPa (5840 psi) and tear strength (tear strength is lower than that desired for commercial practice) and elongation at break are common.

When the film is prepared using a formulation containing 7.5 phr of high styrene-butadiene latex, the tear strength is increased and the tensile strength and elongation are only slightly lost.

Commercial butanepan latex has a low solids content and viscosity. Therefore, commercially available butanepan latex should use a midpoint agent to maintain the suspended state of the hardener particles during aging and dipping operations. Since the acrylonitrile-butadiene copolymer is relatively incompatible with the sodium polyacryl-based reagent, the sodium polyacryl-based reagent tends to flow out of the surface of the primary immersion film. This makes it difficult to apply the secondary immersion layer to the dried primary immersion layer.

In order to eliminate this effect, a process has been developed in which the blend used in the primary dipping contains only a small amount of thickener. The secondary immersion blend incorporates a greater amount of thickener (and high styrene-butadiene copolymer latex), which results in an increase in the viscosity of the immersion liquid to provide the wetting of the primary film and the appropriate overall thickness of the product. This embodiment of the invention is shown in the table below, where Formulation A (containing only acrylonitrile-butadiene latex) is used in the first immersion process and Formulation C (which also contains high styrene styrene-butadiene latex) is the second immersion. Used in the process.

The data in Table 2 show that, as described above, excellent strength and good extensibility required in the preparation for gloves are obtained.

TABLE 1

TABLE 2

Using a double immersion method using Formulation A as the primary immersion solution and Formulation C as the secondary immersion liquid, a slightly larger diameter forming mold [4.0 cm to 3.5 cm (lab-scale male)] was used. Representative properties obtained in a test plant-scale operation for the manufacture of condoms, used, are as follows:

Tensile Strength 35.5 MPa

Elongation at Break 560%

Tear strength 330N / cm

2.2 MPa stress at 100% strain

3.2 MPa stress at 200% strain

Stress at 300% Strain 5.1 MPa

(ii) preparation of condoms and gloves from acrylonitrile isoprene latex

Condom samples are prepared by double immersion as described above. However, glove specimens are prepared in a single immersion / coagulation process using ceramic glove males. In this method, the male is immersed in a solution of the calcium nitrate coagulant dispersed in an aqueous ethanol solution. The solvent is evaporated to deposit the salt on the male surface. The salt coated glove male is immersed once in latex. The deposited latex is dried, cured at 100 ° C. for about 1 hour and then washed.

The physical properties and chemical resistance of the dried rubber film sample are tested. Several formulations are tested. Data for these test formulations is shown in Table 3 below.

TABLE 3

In Formulation D, two salt form accelerators are used to balance the early onset and the delayed response to the use of sulfur. Accelerators in this salt form are zinc diethyldithiocarbamate (ZDC) and zinc salts of mercaptobenzothiazole (ZMBT). The physical properties of the cured film are acceptable for gloves but almost unacceptable in terms of tensile strength and tear resistance for condoms.

M. W. Some early studies of the M. W. Philpott (Natural Rubber Producers Research Association) demonstrated that at 100 ° C. some promoters of very mild sulfur donor type can be activated by the addition of other sulfur containing compounds such as thiourea.

In this way, Formulation E is tested over a wide range of curing times and temperature ranges. A good level of tensile strength is obtained with an increase in tear resistance by a conventional curing process of 1 hour at 100 ° C. Elongation at break is still acceptable for the manufacture of gloves. The concentration of zinc oxide in the formulation also increases. Test data is more consistent with the nature of these formulations. That is, in most rubber compounds, a higher amount of zinc oxide is known to reduce the variation in curing with temperature change.

It is also known to reduce the degradation tendency.

A mixture of acrylonitrile-isoprene latex and high styrene carboxylated styrene-butadiene latex is prepared and the males for gloves and condoms are immersed therein. As previously described with respect to natural rubber mixtures, the addition of high styrene styrene-butadiene copolymers significantly increases the tear strength of the acrylonitrile-isoprene film. However, tensile strength and elongation at break are somewhat reduced.

[General]

Acrylonitrile-isoprene latex, such as butophane latex, is rather difficult to perform a double dipping process because the dried film surface tends to repel the secondary dipping process. This is somewhat offset by the incorporation of high styrene-butadiene latex.

In contrast, acrylonitrile-isoprene latex easily undergoes a coagulant dipping process to obtain a very smooth and uniform dry film by the present technology.

[Chemical Resistance]

Condoms made from butopane latex according to the present invention and commercially available natural rubber condoms are immersed in petroleum jelly (petrolatum) and mineral oil at 37 ° C. (body temperature) for 96 hours. After this time elapses, the condom is removed and the length, width and thickness measured.

Natural rubber condoms that were immersed in petroleum jelly had a 25% increase in each dimension in length, width and thickness. This corresponds to swelling which increased the volume by approximately 90%. The length, width and thickness of the natural rubber condoms immersed in mineral oil increased by 33%, corresponding to a volume increase of about 140%.

In contrast, there is no dimensional increase in butophane condom among other lubricants. The swelling and degradability of gloves and condoms made from both butophane latex and acrylonitrile-isoprene latex are tested in several siffinic chemical liquids. The data in Table 4 shows the swelling rate after immersion for 24 hours at room temperature.

TABLE 4

Testing for condoms is carried out in a production scale apparatus using the double dipping technique as described above wherein the primary dipping liquid contains only acrylonitrile / butadiene latex and the secondary dipping liquid also contains styrene / butadiene latex. The components used for the immersion are shown in Tables 5-7 below:

TABLE 5

1.Zinc diethyl dithiocarbamate

2. Used as thickener and dispersing aid.

TABLE 6

TABLE 7

Typical characteristics of such condoms were found to be:

Claims (3)

Films formed as condoms or gloves consisting of a cured mixture of acrylonitrile with butadiene or isoprene (a) and a high styrene styrene-butadiene copolymer (b) containing at least about 50% by weight of polymerized styrene (which Latex comprising a high styrene-butadiene copolymer (b) in the film is used in a ratio of about 1 to about 15% by weight based on the weight of the copolymer (a) of acrylonitrile and butadiene or isoprene). Film products. The latex film product of claim 1, wherein the copolymer (a) is a carboxylated acrylonitrile / butadiene copolymer. The latex film product of claim 1, wherein the copolymer (a) is a carboxylated acrylonitrile / isoprene copolymer.