Title of Invention

"A METHOD FOR PRESERVATION OF NATURAL RUBBER LATEX USING METHYLOL COMPOUNDS"

Abstract

A method for preservation of natural rubber latex using methylol compound gives neutral pH (pH ~ 7-8), low corrosion and low toxicity natural rubber latex which can be stored for long time and can reduce multivalent metal ions deactivating agent used in the concentrated natural rubber latex production process, wherein said method comprising the steps of : adding methylol compound, wherein at least one of said methylol compound is selected from hydroxymethylaminoacetate, bicyclic oxazolidine, diazolidinyl urea, imidazolidinyl urea and the other formaldehyde releasing agent, in field natural rubber latex; and producing concentrated natural rubber latex by centrifugation, mixing the multivalent metal ion deactivating agent, wherein at least one of said multivalent metal ions deactivating agent is selected from disodium ethylene diamine tetraacetate and tetrasosium ethylene diamine tetraacetate, and mixing anionic surfactant and/or nonionic surfactant.

Full Text

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to methylol compounds used in a method for preservation of natural rubber latex. 2. Background of the Disclosure Natural rubber latex is the sap of a specialized type of cell in Hevea hrasiliensis and other rubber-supplying plants. As such, it is a complex biochemical system. It is therefore not surprising that obvious chemical changes occur shortly after the latex leaves the tree. The first of these changes is that the latex coagulates within a few hours. This process is known as spontaneous coagulation. The time required for coagulation depends upon the ambient temperature and upon the colloid stability of the latex. The second of the obvious changes is putrefaction with the development of bad odours. It is to prevent both these processes occurring that preservation is necessary, Today, ammonia is used as standard preservative for NR latex. Ammonia is a bactericide, enhances colloid stability of the latex, and deactivates magnesium ions. Although ammonia possesses such satisfactory preservative properties, it also has disadvantages. One of disadvantages arises when the preserved latex containing ammonia is processed since ammonia fumes are emitted which pollute or otherwise adversely affect the environment. The emission of the ammonia fumes makes the working environment very unpleasant for the workers or other personnel and may indeed be injurious or hazardous to the health of them, Another problem arising from the emission of ammonia fumes relates to corrosion of factory buildings and roofs. Moreover, because ammonia is easy to evaporate, the amount of ammonia in me latex is also difficult to control. This can affect the qualities of the latex, in particular its variability. Therefore, a continual search has been made for new preservative systems that are not subject to these disadvantages. Many alternatives to ammonia have been considered. US Patent No. 1145352, 1146851, and 1447930 disclose uses of alkalized cresol and alkalized phenol. British Patent No. 294412, 300394, and 300456 disclose uses of sulfonic acid salts. British Patent No. 288268 discloses use of cinnamic acid, butyl alcohol, and sulfuric acid with formaldehyde. British Patent No. 318717 discloses use of sodium pentaborate. US Patent No. 1772753 discloses use of selenious acid and tellulous acid. US Patent No. 1783057 discloses use of ester acid salts such as sodium dicresylphosphate, ammonium diphenylphosphate, or potassium methylsulfate. US Patent No. 1801754 discloses use of aliphatic hydrocarbon such as kerosene and gasoline in combination with phenol. British Patent No. 433116 discloses use of potassium silicate and potassium carbonate. British Patent No. 530836 discloses use of tetrachlorophenol and pentachlorophenol salts. British Patent No. 624917 discloses use of polyethyleneglycol in combination with sodium pentachlorophenate. British Patent No. 530836 discloses use of tetrachlorophenol and pentachlorophenol salts. US Patent No. 2534359 and British Patent No. 661252 disclose use of formaldehyde in combination with a product obtained from a reaction of formaldehyde and arylsulfonic acid salt. US Patent No. 2534370 and British Patent No. 661637 disclose use of formaldehyde in combination with secondary and tertiary amines such as dimethylamine, trimethylamine, diethylamine, triethylamine, and morpholine. British Patent No. 692150 discloses use of halogeno derivatives of hydroxydiphenyl methanes salts. British Patent No. 1036216 discloses use of zinc dialkyl dithiocarbamate such as zinc diethyl dithiocarbamate, ZDEC. British Patent No. 2011933 discloses use of nonionic surfactants. British Patent No. 2283747 and US Patent No. 5840790 disclose use of organic amines in combination with zinc oxide and tetramethylthiuram disulphide, TMTD. Not only the attempts to eliminate ammonia altogether, but the searches for a secondary preservative or an efficient method in order to reduce the level of ammoniation also have been carried out. US Patent No. 1838826 discloses use of ammonia in combination with aromatic sulfonic acid. British Patent No. 368193 discloses addition of formaldehyde followed by ammonia. US Patent No. 2004156 discloses use of ammonia and alkali metal hydroxide in combination with phenol and soap. British Patent No. 463934 discloses use of ammonia in combination with hydroxylamine. US Patent No. 2186202 discloses use of ammonia in combination with alkyl mercuric esters such as ethyl mercury chloride. US Patent No. 2219469 discloses use of ammonia and other bases in combination with arsenic trioxide. British Patent No. 550815 discloses use of ammonia and other bases in combination with nitroparaffin and halogen substituted nitroparaffin. British Patent No. 572134 discloses a method to remove carbon dioxide from the latex in order to increase the efficiency of ammonia. British Patent No. 676188 discloses use of ammonia and other bases in combination with ethylenediamine tetraacetic acid salts. British Patent No. 751106, 752891, and US Patent No. 2802039 disclose methods to remove multivalent metal ions by potassium and sodium hydroxide prior to the addition of ammonia. British Patent No. 788580 discloses use of ammonia in combination with zinc dialkyl dithiocarbamate and anionic or nonionic surfactants. British Patent No. 800089 discloses use of ammonia and other bases in combination with sodium pentachlorophenate and ethylenediamine tetraacetic acid. British Patent No. 811942 discloses use of ammonia in combination with sulphonamide. British Patent No. 821872 discloses use of ammonia in combination with selenium dialkyl dithiocarbamate. British Patent No. 839758 discloses use of ammonia in combination with antibiotics such as streptomycin, chlorotetracycline, and penicillin. British Patent No. 852280 discloses use of ammonia in combination with boric acid. British Patent No. 908283 and US Patent No. 3100235 disclose use of ammonia in combination with 2,2-thiobis(4,6-dichlorophenol). British Patent No. 949364 discloses use of ammonia in combination with 8-hydroxyquinoline, boric acid, and zinc oxide. US Patent No. 2888504 and British Patent No. 854128 disclose use of ammonia in combination with 2-thio-thiazyl compound, 2-thiocarbamyl-thio compound, alkylene polyamine, benzyl trialkyl ammonium compound. British Patent No. 856055 discloses use of ammonia in combination with chlorinated trisodium phosphate and bactericides. British Patent No. 867662 and 874452 disclose use of ammonia in combination with polyamine acid and polycarboxylic acid salts such as 1,2-cyclohexylenediamine tetraacetic acid and uses of borate, iodate, bromate, dichromate, and ferricyanide salts. British Patent No. 881500 discloses use of ammonia in combination with zinc mercaptothiazole such as zinc mercaptobenzothiazole and dispersing agents. British Patent No. 1017532 discloses use of ammonia in combination with boric acid and hydrazine. US Patent No. 5773499 discloses use of ammonia in combination with zinc oxide and water- soluble carboxylic acid salts. British Patent No. 1517025 discloses use of ammonia in combination with zinc oxide and tetramethylthiuram disulphide, TMTD. However, the known methods mentioned above for natural rubber latex preservation are not without disadvantages. For example, the uses of most of those reagents are toxicologically unacceptable and the preserved latex causes corrosion of equipments. Moreover, under certain conditions the reagents such as ZDEC and TMTD spilt off diethylamine or dimethylamine, from which carcinogenic nitrosamines can then be formed due to the action of the almost omnipresent nitrogen oxides or other nitrosation agents. Furthermore, in addition to the bacterial attacking problem, multivalent metal ions, especially magnesium ion, also tend to reduce the colloid stability of the natural rubber latex preserved by the traditional systems. In the present time, it is therefore necessary to remove them prior to the centrifugation process. Not only the preservative is added to the latex, but large amount of multivalent metal ions deactivating agent is also required. SUMMARY OF THE INVENTION This invention relates to method for preservation of natural rubber latex by using methylol compound to prevent rubber coagulation. This method is useful in order to obtain neutral- pH (pH ~ 7-8), low corrosion and low toxicity natural rubber latex which can be stored for long time. Moreover, the method can reduce an amount of multivalent metal ions deactivating agent used in the concentrated natural rubber latex production process. The present invention consist of adding methylol compound to field natural rubber latex and then convert to concentrated natural rubber latex by centrifugation. After that, the concentrated natural rubber latex is added with multivalent metal ions deactivating agent and surfactant. DETAILED DESCRIPTION The overall method for preservation of field natural rubber latex by using methylol compounds will be explained below. 1. The field natural rubber latex is mixed with methylol compound at least one type such as salts of hydroxylmethylaminoacetate (sodium hydroxymethylglycinate and/or potassium hydroxymethylglycinate etc.), bicyclic oxazolidine, diazolidinyl urea, imidazolidinyl urea, and include other chemicals which can release formaldehyde about 0.1-2.0% by weight of the latex. The mixture is then stirred to ensure thorough mixing of the system. 2. The mixtures of field natural rubber latex and methylol compound are converted to concentrated natural rubber latex by centrifugation and then added with multivalent metal ions deactivating agent at least one type of disodium ethylene diamine tetraacetate (Na2EDTA) and tetrasodium ethylene diamine tetraacetate (Na4EDTA) about 0.01-10.0% by weight of the latex. The concentrated latex mixture is stirred and added with anionic surfactant and/or non-ionic surfactant in amount of 0.01-1.0% weight of the latex. This method is useful in order to obtain neutral pH (pH ~ 7-8), low corrosion and low toxicity natural rubber latex which can be stored for long time. Moreover, the method can reduce an amount of multivalent metal ions deactivating agent used in the concentrated natural rubber latex production process. Moreover, the multivalent metal ions deactivating agent can also be added before converting of field natural rubber latex to concentrated natural rubber latex. The method will be explained below. 1. The field natural rubber latex is added with methylol compound at least one type such as salts of hydroxylmethylaminoacetate (sodium hydroxymethylglycinate and/or potassium hydroxymethylglycinate etc.), bicyclic oxazolidine, diazolidinyl urea, imidazolidinyl urea, and include other chemicals which can release formaldehyde. The concentration of methylol compound is about 0.1-2.0% by weight of the latex. The mixture is then stirred to ensure thorough mixing of the system. After that, this mixture is mixed with multivalent metal ions deactivating agent at least one type such as disodium ethylene diamine tetraacetate (Na2EDTA), tetrasodium ethylene diamine tetraacetate (NaiEDTA), sodium carbonate (Na2CO3), sodium metasilicate (Na2SiO3), sodium hydrogen phosphate (Na2HP04), sodium phosphate (Na3PO4), tripolyphosphate (Na5P3O10), potassium hydrogen phosphate (K2HPO4), potassium carbonate (K2CO3), and diarnmonium hydrogen phosphate ((NH4)2HPO4) in amount of 0.01-10.0% weight of the latex. The mixture latex is stirred to ensure thorough mixing of the system at room temperature. 2. The latex mixtures are converted to concentrated natural rubber latex by centrifugation. The concentrated latex mixture is then stirred and added with anionic surfactant and/or non-ionic surfactant in amount of 0.01-1.0% weight of the latex. This method is useful in order to obtain neutral pH (pH ~ 7-8), low corrosion and low toxicity natural rubber latex which can be stored for long time. Moreover, in this method, the methylol compounds can also be use in combination with ammonium, base, and other antiseptic, bactericide, and fungicide such as iodopropynylbutylcarbamate (IPBC) to reduce used methylol compounds quantity. The other preservative is added in amount of 0.01-1.0% weight of the latex. The invention will now be described with reference to the following example. EXAMPLE 1 The field natural rubber latex form rubber tree was divided to the parts and then added with methylol compounds such as sodium hydroxymethylglycinate, diazolidinyl urea, and imidazolidinyl urea in various concentrations. This method might be combined with other preservatives such as iodopropynylbutylcarbamate (IPBC). The latex mixture was stirred to ensure thorough mixing of the system at room temperature. It was found that the latex mixture was neutral pH and had not problem in convert to concentrated latex. Table 1 showed volatile fatty acid number of the latex mixtures. From the results, it could be seen that the field natural rubber latex which was preserved with methylol compounds and/or combined with other perservative had long storage of time. Table 1: Concentration of methylol compounds and volatile fatty acid number of field natural rubber latex with storage time (Table Removed) EXAMPLE 2 The field natural rubber latex form rubber tree was divided to the parts and then added with various bases such as ammonia (NH3), ethanol amine, lithium hydroxide (LiOH), sodium hydroxide (NaOH) and potassium hydroxide (KOH) in combination with sodium hydroxymethylglycinate. The mixture was stirred to homogeneous at room temperature. Table 2 showed that the field natural rubber latex which was preserved by bases in combination with methylol compound had longer storage time than use only the bases. Table 2: Storage time of field natural latex preserved by bases in combination with methylol compound (VFA number (Table Removed) EXAMPLE 3 The field natural rubber latex was added with sodium hydroxymethylglycinate in amount of 0.4 g based on 100 g of latex and centrifuged to obtain concentrated latex. The volatile fatty acid number of the concentrated latex was then measured. Table 3 showed that the volatile fatty acid number of the concentrated latex was low even in long-term storage. Table 3: Volatile fatty acid number of concentrated natural rubber latex (Table Removed) EXAMPLE 4 Sodium hydroxymethylglycinate was added to field natural rubber latex in amount of 0.4 g based on 100 g of latex and stirring. The mixture was then centrifuged to obtain concentrated natural rubber latex. Disodium ethylene diamine tetraacetate and sodium dodecyl sulfate were added to concentrated natural rubber latex in amount of 0.3 g and 0.25 g based on 100 g of latex, respectively. The mixture was stirred and left at room temperature. Toxicity of concentrated natural rubber latex was tested by agar overlay. Table 4 showed that concentrated natural rubber latex according to this invention is not toxic comparing with high ammonia latex and low ammonia/TMTD/ZnO. Table 4: Toxicity test of concentrated natural rubber latex (Table Removed) EXAMPLE 5 Sodium hydroxymethylglycinate was added to field natural rubber latex in amount of 0.4 g based on 100 g of latex and stirring. The mixture was then centrifuged to obtain concentrated natural rubber latex. Disodium ethylene diamine tetraacetate and sodium dodecyl sulfate were added to concentrated natural rubber latex in amount of 0.3 g and 0.25 g based on 100 g of latex, respectively. The mixture was stirred and left at room temperature. Corrosion to mild steel and stainless steel of concentrated natural rubber latex was tested. Table 5 showed that the corrosion to mild steel and stainless steel of concentrated natural rubber latex according to this invention is lower than that of high ammonia latex and low ammonia/TMTD/ZnO. Table 5: Corrosion to mild steel and stainless steel of concentrated natural rubber •latex (Table Removed) WE CLAIM: 1. A method for preservation of natural rubber latex using methylol compound gives neutral pH (pH ~ 7-8), low corrosion and low toxicity natural rubber latex which can be stored for long time and can reduce multivalent metal ions deactivating agent used in the concentrated natural rubber latex production process, wherein said method comprising the steps of : 1.1 adding methylol compound, wherein at least one of said methylol compound is selected from hydroxymethylaminoacetate, bicyclic oxazolidine, diazolidinyl urea, imidazolidinyl urea and the other formaldehyde releasing agent, in field natural rubber latex in the amount of 0.1 to 2.0 g based on 100 g of latex ; and 1.2 producing concentrated natural rubber latex by centrifugation, mixing the multivalent metal ion deactivating agent, wherein at least one of said multivalent metal ions deactivating agent is selected from disodium ethylene diamine tetraacetate and tetrasosium ethylene diamine tetraacetate, in the amount of 0.01 to 10.0 g based on 100 g of latex and mixing anionic surfactant and/or nonionic surfactant in the amount of 0.01 to 1.0 g based on 100 g of latex. 2. The method as claimed in claim 1, wherein the addition of multivalent metal ions deactivating agent before concentrated natural latex production comprising the steps of: 2.1 adding methylol compound, wherein at least one of said methylol compound is selected from hydroxymethylaminoacetate, bicyclic oxazolidine, diazolidinyl urea, imidazolidinyl urea and the other formaldehyde releasing agent, in field natural rubber latex in the amount of 0.1 to 2.0 g based on 100 g of latex and then adding multivalent metal ions deactivating agent, wherein at least one of said multivalent metal ions deactivating agent is selected from disodium ethylene diamine tetraacetate and tetrasodium ethylene diamine tetraacetate, sodium carbonate, sodium metasilicate, sodium hydrogen phosphate, sodium phosphate, tripolyphosphate, potassium hydrogen phosphate, potassium carbonate and diammonium hydrogen phosphate in the amount of 0.01 to 10.0 g based on 100 g of latex; and 2.2 producing concentrated natural rubber latex by centrifugation and then adding anionic surfactant and/or non-ionic surfactant in the amount of 0.1 to 1.0 g based on 100 g of latex. 3. The method as claimed in claim 1, wherein at least one of said hydroxymethylaminoacetate is selected from sodium hydroxymethylglycinate and potassium hydroxymethylglycinate.

Documents:

1141-DEL-2007-Abstract-(02-03-2012).pdf

1141-del-2007-abstract.pdf

1141-DEL-2007-Claims-(02-03-2012).pdf

1141-del-2007-claims.pdf

1141-DEL-2007-Correspondence Others-(02-03-2012).pdf

1141-DEL-2007-Correspondence-Others-(26-03-2010).pdf

1141-del-2007-correspondence-others.pdf

1141-DEL-2007-Description (Complete)-(02-03-2012).pdf

1141-del-2007-description (complete).pdf

1141-del-2007-form-1.pdf

1141-del-2007-form-13.pdf

1141-del-2007-form-18.pdf

1141-DEL-2007-Form-2-(02-03-2012).pdf

1141-del-2007-form-2.pdf

1141-DEL-2007-Form-26-(26-03-2010).pdf

1141-DEL-2007-Form-3-(02-03-2012).pdf

1141-del-2007-form-3.pdf

1141-del-2007-form-5.pdf

1141-DEL-2007-GPA-(02-03-2012).pdf

1141-del-2007-gpa.pdf

1141-DEL-2007-Petition-137-(02-03-2012).pdf