DESC: FIELD OF INVENTION
[0001] The present invention relates to synthetic latex composition and manufacture of dip molded articles there from. More particularly, the present invention relates to latex compositions that obviates addition of accelerators and sulfur-based cross linking agents during dip molding.
BACKGROUND
[0002] It is known that rubber gloves are extensively used in various fields which include housekeeping, medical, food and the like. One of the problems associated with gloves manufactured using natural rubber latex is that they contain proteins which cause an allergic reaction such as Type I hypersensitivity. As a result, many manufacturers have shifted to various synthetic materials for manufacture of gloves. These materials do not contain any proteins. Such synthetic materials include nitrile latex, carboxylated nitrile latex, polychloroprene latex, and polybutadiene latex.
[0003] Methods of manufacture of gloves and other articles using the above mentioned synthetic lattices employ sulfur as a vulcanizing agent. Presence of sulfur imparts a peculiar odor to the gloves which is highly undesirable. Further, these methods also employ accelerators such as dithiocarbamate, tetramethylthiuram disulfide (TMTD) and mercaptobenzothiazole (MBT) for the purposes of enhancing the rate of vulcanization. Trace amounts of accelerators in the end products leads to type IV chemical allergic reactions in humans.
[0004] In view of the above, several attempts have been made to develop processes for preparation of synthetic lattices and subsequent manufacture of articles like gloves there from that specifically obviate the use of sulfur and accelerators.
[0005] For instance, WO2011068394 discloses a composition for producing an elastomeric thin film comprising carboxylated acrylonitrile polybutadiene latex which is vulcanized without the use of conventional sulfur and accelerators.

[0006] Further, there is disclosed in US8975351 a latex resin composition for rubber gloves without sulfur and a vulcanization accelerator and a method of manufacturing dip-formed article using the composition. The composition comprises a conjugated diene monomer; an ethylenically unsaturated nitrile monomer; an ethylenically unsaturated acid monomer; an ethylenically unsaturated monomer copolymerizable with the ethylenically unsaturated nitrile monomer and the ethylenically unsaturated acid monomer; and a reactive compound including two or more reactive groups.

[0007] There still exists a need for a dipping latex composition that is cost effective, easy to prepare and which enables production of dipped articles with desired tensile strength without addition of cross-linking agents and sulfur-based across linking agents.

OBJECTS
[0008] Accordingly, it is one of the objects of the present invention to provide a dipping co-polymer latex composition that is devoid of accelerators and sulfur-based compounds.
[0009] It is yet another object of the present invention to provide gloves and other dip molded articles that do not cause allergies or which significantly reduce the probability of allergic reactions in end users.

SUMMARY
[0010] In one aspect of the present invention, there is provided a co-polymer latex composition for manufacture of dip-molded articles without addition of accelerators and sulfur-based cross-linking agent. The composition comprises a co-polymer emulsion obtained by emulsion polymerization of 62 to 74phm a conjugated diene monomer, 22 to 30phm ethylenically unsaturated nitrile monomer, 4 phmto 8phm of an ethylenically unsaturated acid monomer, and at least one alkyl ester of ethylenically unsaturated acid in an amount ranging from 0.5 to 4phm.

[0011] In another aspect of the present invention, there is provided a method of preparing the co-polymer latex composition for manufacture of dip-moulded articles without addition of accelerator and sulfur-based cross-linking agent. Typically, the method comprises:
additing a first portion of reagents comprising water between 85 to 95phm, conjugated diene monomer between 62 to 74phm, ethylenically unsaturated nitrile monomer between 22 to 30 phm, alkyl ester of ethylenically unsaturated acid between 0.5phm to 5 phm, ethylenically unsaturated acid monomer between 1 to 5phm, and emulsifier between 0.2 to 1 phm to the reactor and agitating the resulting reaction mixture till the temperature reaches between 30 oC to 38oC;
- initiating polymerization by addition of an initiator to the reactor in an amount from 0.1phm to 0.5phm;
-gradually adding a second portion of reagents comprising ethylenically unsaturated acid monomer between 1 to 5 phm; emulsifier between 1 to 3phm to the reaction mixture after commencement of polymerization at a temperature ranging between 30 oC to 38oC till the conversion reaches up to 55% to 65%;
-raising the temperature of the polymerization mixture to 55 to 60oC and continuing the polymerization; and
-terminating polymerization reaction by addition of 0.03 to 0.1 phm diethyl hydroxylamine and optionally adjusting the pH after termination by addition of potassium hydroxide.
[0012] In still another aspect of the present invention, there is provided a dipping co-polymer latex composition prepared by addition of potassium hydroxide and zinc oxide in the co-polymer latex composition. Typically, the dipping composition is characterized by pH ranging from 9 to 10.5 and % solid content ranging from 20% to 30%.
[0013] In a further aspect of the present invention, there is provided a dip-molded article prepared from the dipping co-polymer latex composition. The latex material of the dipped article is typically characterized by tensile strength ranging between 15MPa and 30 MPa; % elongation ranging from 500% to 700%; and 500% modulus ranging from 7 to 15.
DESCRIPTION
Definitions:
[0014] The terms and phrases as indicated in quotation marks (“ ”) in this section are intended to have the meaning ascribed to them in this ‘Definitions’ section applied to them throughout this document, including in the claims, unless clearly indicated otherwise in context.
[0015] “Accelerators” means organic compounds incorporated in the latex during the manufacture of dip molded articles, which include but are not limited to chemical class of thiuram, carbamate and thiazoles; for example ZDBC, ZDEC, TMTD and the like.
[0016] “Sulfur based cross-linking agents” means one or more sulfur based compounds incorporated in the latex during the manufacture of dip molded articles which include but are not limited to sulfur monochloride, morpholindisulphide and the like.
[0017] ‘phm’ means “parts per hundred monomers.‘phr’ means “parts per hundred rubber”.“p.b.w” means “parts by weight.” “NVM” means “non-volatile matter.”
[0018] In one aspect the present invention, there is provided a co-polymer latex composition that obviates the need for addition of accelerator and sulfur-based cross-linking agent in the manufacture of dip molded articles during compounding stage of the manufacturing process. The copolymer latex composition of the present invention prepared by emulsion polymerization, comprises 62 to 74phm conjugated diene monomer, 22 to 30 phm an ethylenically unsaturated nitrile monomer, 4phm to 8phm of an ethylenically unsaturated acid monomer, and at least one alkyl ester of ethylenically unsaturated acid in an amount ranging from 0.5phm to 4 phm.

[0019] Typically, the conjugated butadiene monomer is selected from the group consisting of 1, 3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and isoprene. In an exemplary embodiment, the conjugated butadiene is 1, 3-butadiene.
[0020] The ethylenically unsaturated nitrile monomer employed in the base polymer is typically at least one selected from the group consisting of acrylonitrile, methacrylonitrile, a-cyanoethylacrylonitrile, a-chloronitrile and fumaronitrile.

[0021] The ethylenically unsaturated carboxylic acid monomer is typically selected from the group consisting of acrylic acid, methacrylic acid, sorbic acid, ß-acryloxy-propionic acid, ethacrylic acid. In accordance with an exemplary embodiment of the present invention, the carboxylic acid monomer is methacrylic acid.

[0022] In their quest to arrive at a co-polymer latex composition that does not require any accelerators or sulfur-based compounds for cross-linking and curing (during compounding), the inventors of the present invention conducted a series of experiments. Addition of an alkyl ester of ethylenically unsaturated acid to the carboxylated acrylonitrile-butadiene in an amount ranging between 0.5 to 4phm(parts per hundred monomer) provides a co-polymerlatex composition that does not require addition of any accelerators or sulfur-based compounds for cross-linking at compounding stage.

[0023] Typically, the alkyl ester of ethylenically unsaturated acid is at least one selected from the group consisting of allyl acrylate, allyl methacrylate, diallyl maleate, diallylfumarate, diallylitaconate, allyl acid maleate, allyl acid fumarate, and allyl acid itaconate. In accordance with an exemplary embodiment of the present invention, allyl methacrylate is used.

[0024] It has been observed that as the proportion of alkyl ester of ethylenically unsaturated acid goes on increasing from 0.5 phm, the tensile strength as well as elongation of the resulting latex material goes on increasing till the proportion reachesupto 4phm. However, further addition of this compound does not result any further enhancement in advantageous properties of the resulting latex materials such as tensile strength.

[0025] Without being bound by theory, it has been found that the alkyl ester of ethylenically unsaturated acidserves the role of an internal cross-linker during the emulsion polymerization by forming covalent bonds across the polymer backbone of the nitrile polymer. This covalent cross-linking improves the tensile strength of the resulting latex material.

[0026] Typically, the co-polymer latex emulsion is a water-based emulsion characterized by pH ranging from 6 to 10, preferably from 7 to 9. Typically, % solid content of the co-polymer latex composition ranges from 30% to 50% by weight, preferably, from 40% to 48% by weight.

[0027] Typically, the viscosity of the co-polymer latex emulsion is in the range from 10 to 100cp.Surface tension of the base polymer emulsion ranges from 35-45 dyne/cm. Typically, the particle size of base polymer emulsion ranges from 60 to 300 nm, preferably from 100 to 150nm and most preferably from 110 to 130nm as measured by particle size analyzer. Typically, the insoluble Methyl ethyl ketone components in theco-polymer latex emulsion range from 40% to 70%.

[0028] The emulsion polymerization process for preparation of the co-polymer latex composition in accordance with the present invention substantially improves the extent of polymerization (conversion) up to 85%, preferably up to 95% and most preferably up to 98% conversion.

[0029] The method of emulsion polymerization to obtain the co-polymer latex composition of the present invention involves the addition of reagents to the reactor in two portions.

[0030] The first portion of the reagents that are introduced to the polymerization reactor comprise water between 85 to 95phm, conjugated diene monomer between 62 to 74phm, ethylenically unsaturated nitrile monomer between 22 to 30 phm, alkyl ester of ethylenically unsaturated acid between 0.5phm to 5 phm, ethylenically unsaturated acid monomer between 1 to 5phm, and emulsifier between 0.2 to 1 phm.

[0031] The reaction mixture is agitated till the temperature reaches between 30 oC to 38oC.At this stage, polymerization initiator is added to the reaction mixture to initiate the polymerization. Once the polymerization is initiated, the second portion of the reagents is introduced to the polymerization mixture.

[0032] Typically, the second portion of the reagents that are introduced to the reactor after commencement of polymerization comprise ethylenically unsaturated acid monomer between 1 to 5 phm ; emulsifier between 1 to 3phm. These are added gradually at a temperature ranging between 30 oC to 38oC till the conversion reaches up to 55% to 65%.

[0033] Once the conversion reaches the above limit, the temperature of the reaction mixture is increased between 55 to 60oC and the polymerization is continued till conversion rate reaches up to 85%, preferably 95% and most preferably upto 98%.
[0034] Subsequently, the polymerization reaction is terminated by addition of 0.03 to 0.1 phmdiethyl hydroxylamine and the pH is optionally adjusted by addition of potassium hydroxide.
[0035] Typically, the ratio of the amount of ethylenically unsaturated acid monomer added before and after initiation of polymerization ranges from 3:1 to 1:3. The manner of addition of emulsifier and ethylenically unsaturated acid monomer as well as their quantities added before and after initiation of polymerization decide the characteristics of the co-polymer latex composition such as particle size, tensile strength and surface tension.
[0036] Typically, the initiator is selected from the group consisting of inorganic peroxide such as potassium persulphate, sodium per sulphate, ammonium per sulphate, organic peroxides such as t-butyl peroxide, p-menthanehydroperoxide, inorganic peroxide in combination with reducing agent such as sodium metabisulphite, sodium formaldehyde sulfoxylate or organic peroxide in combination with said reducing agent. Typically, the amount of initiator ranges from0.1 to 1.0phm.

[0037] In one embodiment, the initiator is potassium per sulphate in combination with sodium formaldehyde sulfoxylate. In another embodiment, the initiator is a combination of potassium per sulphate, sodium formaldehyde sulfoxylate and sodium per sulphate.

[0038] Typically, the emulsifier is an anionic surfactant. In accordance with exemplary embodiment of the present invention, the anionic surfactant employed for emulsion polymerization is selected from the group consisting of surfactant having a pair of sulfonate groups on a diphenyl oxide backbone, sodium dodecyl benzene sulfonate, aliphatic sulfonic acid salt, higher alcohol sulfuric acid ester salt, olefin sulfonic acid salt, and alkyl ether sulfuric acid ester salt. Typically, the amount of surfactant ranges from 0.1 to 2.0 phm.

[0039] The process of emulsion polymerization optionally involves addition of one or more additives selected from the group consisting of a molecular weight modifier, a chelating agent wetting/dispersing agent and anti-oxidants.

[0040] The molecular weight modifier/regulator employed in the polymerization reaction may be selected from the group consisting of mercaptan such as methylstyrene, t-dodecyl mercaptan, n-dodecyl mercaptan, and octylmercaptan; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, methylene bromide, combinations thereof and the like.Typically, the amount of molecular weight modifiers varies from 0.2 to 1.0 phm.

[0041] The dispersing agent & wetting agent in the said latex composition improves the dispersibility of curing additives in dipping composition. Further, they also improve performance of dipped articles. Typically, the dispersing agent is selected from the group consisting of anionic water soluble polymer such as sodium salt of polyacrylic acid, sodium salt of polymethacrylic acid, styrene-itaconic acid copolymers; and N-vinyl-2-oxazolidinone-maleic anhydride copolymers.
[0042] Typically, the wetting agent is selected from the group that includes Polyether siloxanes, alkyl aryl polyether alcohols, polyethersiloxanes in combination with defoamer.Typically, the amount of dispersing and wetting agent varies from0.1 to 2.0 phm.

[0043] The antioxidant in the said latex composition is at least one selected from the group consisting of butylated phenols such as phenols, alkylated phenols, arylated phenols, bisphenol A, isocyanurates, butyl phenols, fortified phenols, phosphited phenols, butylated phenols, phenolics, reaction products of p-cresol and cyclopentadiene, styrenated phenols, hydroquinolines and dithiocarbamates.Typically, the amount of antioxidant varies from 0.2 to 1.0 phm.
[0044] A chelating agent may be employed during the emulsion polymerization process. Typically, EDTA is used as a chelating agent in an amount ranging from0.01 to 0.05% by phm.

[0045] The dipping co-polymer latex composition devoid of accelerator and sulfur-based cross-linking agent in accordance with the present invention is prepared by admixing the base co-polymer latex composition as described herein above with potassium hydroxide to increase the pH ranging between 9.5 to 11 and incorporating zinc oxide for cross-linking; and subjecting the resulting admixture to homogenization in a homogenizer for a period ranging from4 to 8 hours at a temperature ranging from 25 to 35°C under constant agitation in a dipping tank.

[0046] The dipping co-polymer latex composition in accordance with the present invention is characterized by pH ranging from 9 to 11 and % solid content ranging from 20% to 30% and viscosity in the range from10 to 50 cps.
[0047] In accordance with still another aspect of the present disclosure there is provided a process for manufacture of gloves and other articles using the dipping co-polymer latex composition of the present invention.
[0048] Typically, the method step of preparation of a dipping composition comprises: admixing the latex of the present disclosure with water, potassium hydroxide,zinc oxide and one or more additives in a homogenizer for a period ranging from4 to 8 hours at a temperature ranging from20 to 45°C, preferably from 25 to 35°Cunder constant agitation in a dipping tank. Typically, the dipping composition is characterized by pH ranging from 9 to 11,solid content ranging from30 to 40%

[0049] Typically, the method of preparing the mould involves washing it with hot water and pre-heating it in a hot air oven at a temperature ranging from 60 to 80oC for a period ranging from 40 to 150 seconds. Dipping is carried out two times. In the first instance, the hot mould is dipped into 40% coagulant solution at a temperature ranging from 40 to 70oC for a period ranging from 10 to 100seconds. The mould is then dried in a hot air oven at 80oC for at least 5 min, preferably for at least 2min.
[0050] In the second instance, the mould is dipped at a room temperature for 15- 150 seconds in the dipping co-polymer latex composition of the present invention. The mould is the removed and it is subjected to leaching in hot water at 50oC for at least 5 minutes, preferably for at least 3 minutes. After leaching, the mould is dried in a hot air oven at 80oC for about 10 mins, preferably for at least 5 minutes.
[0051] Curing is typically carried out in an oven at100-130oC for about 25 minutes. The cured articles are stored at room temperature and the formed film is stripped.
[0052] The invention will now be described with the following non-limiting examples.

EXAMPLES
Example 1a
[0053] Preparation of co-polymer latex composition and dipping composition of the present invention with 0.5 phm allyl methacrylate (AMA)
[0054] To a pressure-tight autoclave polymerization reactor were added 92 phm Deionized water (DI water), 0.2 phm sodium sulphate, 0.02 phmEthylenediaminetetraacetic acid(EDTA), 0.3 phmDowfax DB 45TM surfactant (anionic surfactant), 2.5 phmmethacrylic acid, 28 phm acrylonitrile, 67phm butadiene, 0.5 phmallyl methacrylate and 0.6phm t-dodecyl mercaptant (TDM), 0.2phm potassium persulphate and 0.2 phm sodium formaldehyde sulfoxylate, and then the polymerization reaction was initiated when the temperature reached to 35oC.
[0055] After initiation of reaction, emulsifier solution of 2.5 phmmethacrylic acid and 1.5 phm Dowfax DB 45 surfactant solution mixture was introduced and the resulting mixture was stirred at 35oC. When the degree of polymerization conversion of the total of the monomers in the polymerization reaction system reached 62%, the temperature was raised to 60oC to continue the polymerization. When the polymerization conversion reached 98%, 0.1 Phmdiethyl hydroxylamine was added to the reaction mixture to stop the polymerization.
[0056] After completion of the polymerization reaction, the un-reacted monomers were stripped to remove un-reacted monomers, a 5% potassium hydroxide solution and Bostex 24, a butylated product of p-cresol and dicyclopentadiene, as an antioxidant were added to obtain the co-polymer latex composition of the present invention. Total solid content of the co-polymer latex composition was 44%. pH of the co-polymer latex composition was found out to be 8. Viscosity was measured by Brookfield viscometer and it was found out to be 30cp while NVM was 42. Surface tension of the co-polymer latex composition was found to be 42 dyne/cm and particle size ranged from 110 to 130 nm as measured by particle size analyzer. Further, the insoluble Methyl ethyl ketone components were measured and they were found to be 65%.
[0057] Example 1 b
Preparation of dipping composition from the co-polymer latex composition
1 kg of the co-polymer latex composition as prepared in example 1a was introduced to compounding tank. 2%KOH was then added under continuous agitation to the co-polymer latex composition to increase the pH to 9.00. Water was added to the admixture to obtain the dipping composition with total solid content of 30%. Viscosity of the compounded dipping composition was found to be 8cps. The composition of the compounded dipping composition is provided below in Table 1.
Recipe
phr Qty. Solids Final Quantity in
Recipe (phr) Dry
Composition in Example 1a 42% 1000.00 420
Initial KOH 1.2 phr 2% 252.00 5.04
ZnO 2.5 phr 50% 21.00 10.5
Water For 30% solids 179.00
Total 1452.00 435.54
% Solids 30.00

Example 1c
[0058] Manufacture of Dip Molded article from the dipping composition without addition of accelerators and sulfur based cross-linking agents:
[0059] Coagulating medium with following composition was prepared.
Calcium nitrate 30 p.b.w
Water70 p.b.w and
Wetting agent 0.1 p.b.w
[0060] The dipping composition as prepared in Example 1b was used for dip molding. Mold was washed in hot water and the washed mold was preheated in hot air oven at 80oC for 2 min. The hot mold was dipped into 30% coagulant solution a temperature ranging of 60oC for one minute. The dipped mold was then dried again in hot air oven at 80oC for 3 min. The dried mould was then dipped in the compounded dipping composition as prepared in Example 1b at room temperature for 30 seconds. The dipped mould was subsequently removed subjected to leaching in hot water at 50 oC for at 3 minutes. The leached mold was dried in a hot air oven at 80oC for about 5 mins. The mold was subsequently cured in oven at120oC for 25 minutes.
[0061] The latex material obtained after dipping was evaluated and tested for tensile strength and elongation modulus. Also, the impact of pH of the dipping composition on tensile strength and elongation was studied. Accordingly, 4 different compounded dipping compositions with pH between 9 and 10.5 were prepared and the tensile strength and elongation were measured for respective end products.

Table 2(Example 1 with 0.5 phm allyl methacrylate)
Compound pH ZnO level Tensile strength % Elongation 100 % Modulus 300% Modulus 500% Modulus
9 2.5 phr 15 588 2.35 3.14 5.84
9.5 2.5 phr 18 595 2.51 3.21 5.94
10 2.5 phr 21 650 2.78 3.35 6.28
10.5 2.5 phr 22 628 2.84 3.78 7.23

[0062] Example 2
[0063] Preparation of co-polymer latex composition and dipping composition without allyl methacrylate
[0064] The same reactants and additives as used in Example 1 were used and the same procedure was followed except that allyl methacrylate was not added. The latex obtained after dip molding was tested for its tensile strength and elongation modulus.
Table 3 (Example 2; without allyl methacrylate)
Compound pH ZnO level Tensile strength % Elongation 100 % Modulus 300% Modulus 500% Modulus
9 2.5 phr 10 788 2.34 3.01 5.14
9.5 2.5 phr 12 775 2.54 3.09 5.32
10 2.5 phr 14 750 2.67 3.16 5.58
10.5 2.5 phr 15 730 2.81 3.34 5.71

[0065] Examples 3-6,
[0066] The same procedure as provided in Example 1 along with same reactants and additives was followed except that the proportion of allyl methacrylate was gradually increased from 0.5phm (Example 1) to 1phm, 2phm , 3phm and finally 4 phm(corresponding to examples 3 to 6). The latex material obtained after dipping were evaluated and tested for tensile strength and elongation modulus. Also, for each example, the impact of pH of the dipping composition on tensile strength and elongation was studied. Accordingly, 4 different compounded dipping compositions with pH between 9 and 10.5 were prepared and the tensile strength and elongation were measured for respective end products.
[0067] Table4-7 below provides the details of these tensile strength and elongation modulus of the latex prepared from compositions prepared in examples 3 to 6.
[0068] Table 4
Example 3 with 1phm allyl methacrylate(AMA )
Compound pH ZnO level Tensile strength % Elongation 100 % Modulus 300% Modulus 500% Modulus
9 2.5 phr 18 597 2.02 3.22 9.85
9.5 2.5 phr 20 589 2.15 3.38 9.92
10 2.5 phr 23 630 2.19 3.56 10.07
10.5 2.5 phr 23 617 2.16 3.61 11.12

Table 5
Example 4 with 2 phm AMA
Compound pH ZnO level Tensile strength % Elongation 100 % Modulus 300% Modulus 500% Modulus
9 2.5 phr 19 573 2.57 4.92 10.86
9.5 2.5 phr 22 586 2.62 5.19 11.08
10 2.5 phr 25 605 3.16 5.56 11.32
10.5 2.5 phr 26 591 3.31 5.68 12.45

Table 6
Example 5 with 3 phm AMA
Compound pH ZnO level Tensile strength % Elongation 100 % Modulus 300% Modulus 500% Modulus
9 2.5 phr 20 535 3.32 5.73 12.08
9.5 2.5 phr 22 538 3.39 5.81 12.19
10 2.5 phr 26 565 3.51 5.92 13.51
10.5 2.5 phr 26 543 3.68 6.12 14.75

Table 7
Example 6 with 4 phm AMA
Compound pH ZnO level Tensile strength % Elongation 100 % Modulus 300% Modulus 500% Modulus
9 2.5 phr 20 531 2.64 4.73 13.54
9.5 2.5 phr 23 528 2.72 4.86 13.91
10 2.5 phr 25 545 2.86 5.14 16.23
10.5 2.5 phr 26 532 2.95 5.31 16.84

[0069] The method of emulsion polymerization to prepare co-polymer latex composition of the present invention significantly improves conversion up to 98%. The alkyl ester of ethylenically unsaturated acid in the composition not only obviates the use of sulfur but it also reduces maturation time. Further, it also improves the compounding stability of the composition thereby facilitating its further processing. This not only saves costs but also improves productivity. Gloves and other articles of the present disclosure exhibit desired tensile strength with excellent softness. Further, they posses balanced mechanical properties on account of low modulus and flexibility. From end user’s perspective, the gloves do not posses any undesirable odor and they do not cause any allergy.

[0070] Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
[0071] The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

[0072] Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.

[0073] The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary.

[0074] While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the invention herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

,CLAIMS:[0075] We claim:
1. A co-polymer latex composition for manufacture of dip-molded articles without addition of accelerator and sulfur-based cross-linking agent; said composition comprising:
a co-polymer emulsion obtained by emulsion polymerization of 62 to 74phm a conjugated diene monomer, 22 to 30 phm ethylenicallyunsaturated nitrile monomer, 4 phm to 8 phm of an ethylenically unsaturated acid monomer, and at least one alkyl ester of ethylenically unsaturated acid in an amount ranging from 0.5 to 4 phm.

2. A co-polymer latex composition as claimed in claim 1; wherein the conjugated diene monomer unit is at least one selected from the group consisting of 1, 3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and isoprene.

3. A co-polymer latex composition as claimed in claim 1; wherein the ethylenically unsaturated nitrile monomer unit is at least one selected from the group consisting of acrylonitrile, methacrylonitrile, a-cyanoethylacrylonitrile, a-chloronitrile and fumaronitrile.

4. A co-polymer latex composition as claimed in claim 1; wherein the ethylenically unsaturated acid monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, sorbic acid, ß-acryloxy-propionic acid, ethacrylic acid.

5. A co-polymer latex composition as claimed in claim 1; wherein the alkyl ester of ethylenically unsaturated acid is at least one selected from the group consisting of allyl acrylate, allyl methacrylate, diallyl maleate, diallylfumarate, diallylitaconate, allyl acid maleate, allyl acid fumarate, and allyl acid itaconate.

6. A co-polymer latex composition as claimed in claim 1; wherein the alkyl ester of ethylenically unsaturated acid is allyl methacrylate.

7. A co-polymer latex composition as claimed in claim 1; wherein the co-polymer latex composition is characterized by viscosity ranging from 10 to 50cp ; surface tension ranging from 40-44 dyne/cm and particle size ranging from 100 to 150 nm as measured by particle size analyzer.

8. A co-polymer latex composition as claimed in claim 1; wherein the co-polymer latex composition is characterized by insoluble Methyl ethyl ketone components are in the range from 60% to 70%.

9. A dipping co-polymer latex composition prepared by addition of potassium hydroxide and zinc oxide in the co-polymer latex composition as claimed in any of the claims above; said dipping composition characterized by pH ranging from 9 to 10.5 and % solid content ranging from 20% to 30%.

10. A dip-molded article prepared from the dipping co-polymer latex composition as claimed in claim 9, characterized by tensile strength ranging between 15MPa and 30 MPa; % elongation ranging from 500% to 700% ; and 500% modulus ranging from 7 to 15.

11. A method of preparing co-polymer latex composition for manufacture of dip-moulded articles without addition of accelerator and sulfur-based cross-linking agent; said method comprising:
-adding a first portion of reagents comprising water between 85 to 95phm, conjugated diene monomer between 62 to 74phm, ethylenically unsaturated nitrile monomer between 22 to 30 phm, alkyl ester of ethylenically unsaturated acid between 0.5phm to 5 phm, ethylenically unsaturated acid monomer between 1 to 5phm, and emulsifier between 0.2 to 1 phm to the reactor and agitating the resulting reaction mixture till the temperature reaches between 30 oC to 38oC;
- initiating polymerization by addition of an initiator to the reactor in an amount from 0.1phm to 0.5phm;
-gradually adding a second portion of reagents comprising ethylenically unsaturated acid monomer between 1 to 5 phm; emulsifier between 1 to 3phm to the reaction mixture after commencement of polymerization at a temperature ranging between 30 oC to 38oC till the conversion reaches upto 55% to 65%;
-raising the temperature of the polymerization mixture to 55 to 60oC and continuing the polymerization; and
-terminating polymerization reaction by addition of 0.03 to 0.1 phmdiethyl hydroxylamine and optionally adjusting the pH after termination by addition of potassium hydroxide.

12. A method of preparation of co-polymer latex composition as claimed in claim 11, wherein the ratio of the amount of ethylenically unsaturated acid monomer added before and after initiation of polymerization ranges from 3:1 to 1:3.

13. A method of preparation of co-polymer latex composition as claimed in claim 11, wherein the emulsion polymerization is terminated upon at least 85% conversion, preferably at least 95% and most preferably at least 98% conversion.

14. A method of preparation of co-polymer latex composition as claimed in claim 11, wherein the method further comprises :
-admixing the co-polymer latex composition with potassium hydroxide to increase the pH ranging between 9.5 to 11;
-incorporating zinc oxide for cross-linking; and
- subjecting the resulting admixture to homogenization in a homogenizer for a period ranging from4 to 8 hours at a temperature ranging from 25 to 35°Cunder constant agitation in a dipping tank to obtain a dipping composition.

15. The method of preparing a dipped article from the dipping co-polymer latex composition as claimed in claim 9 without using accelerator and sulfur compounds, said method comprising:
? washing a mold with hot water and pre-heating it in a hot air oven at a temperature ranging from 60 to 80oC for a period ranging from 40 to 150 seconds;
? dipping the hot mould into 30 % coagulant solution at a temperature ranging from 40 to 70oC for a period ranging from 10 to 100seconds;
? drying the hot mould in a hot air oven at 80oC for at least 5 min, preferably for at least 2min;
? dipping the mould at room temperature for 15- 150seconds in the dipping composition;
? removing the mould and subjecting to leaching in hot water at 50 oC for at least 5 minutes, preferably for at least 3 minutes.
? drying the mould in a hot air oven at 80oC for about 10mins, preferably for at least 5 minutes and curing in an oven at100-130oC for about 25 minutes.

Dated this 7th Day of May 2016.

MANISH BHANGALE
APPLICANT’S PATENT AGENT (IN/PA 1837)
NOVO IP