|Title of Invention||
A PROCESS OF MANUFACTURE OF PVA SPONGE
|Abstract||A Process of preparing three - dimensional open cell structured polyvinyl acetate sponge comprising the following steps, a) Preparing polyvinyl acetate emulsion by charging conventional high speed mixtures using water, and / or solvent under continuous stirring for a period of 10 to 15 minutes at a constant temperature; b) Acetalistion of polyvinyl acetate emulsion obtained at step (a), added pore forming agent to make water soluble porous structure; c) Frothing followed by washing;|
|Full Text||FORM - 2
The Patent Act, 1970
(39 of 1870)
(Section 10; Rule 13)
1) "A PROCESS OF MANUFACTURING PVA SPONGE",
2) MR, CHETAN RAVINDRA MEHTA
(Indian National) having office at 701, Shilpa Apts., Jagdusha Nagar, Ghatkopar (West), Mumbai - 400 086.
The following specification describes the nature of this invention & the manner in which it is performed:
The present invention relates to a Process of manufacturing PVA Sponge.
Conventionally, many types of porous products such as natural sea sponge, cork, rubber sponge, viscose sponge, PU (Polyurethane) foam and polyethylene sponge are presently available in the market. These are generally called sponges or foams. The difference in the properties of these products is basically due to the difference in the raw materials and the pore forming mechanism used. The manufacturing process of conventional PU foams is explained below.
Polyurethanes are used to make flexible and rigid foams. PU foams are generally formed by mixing two primary ingredients during processing - Polyisocyanate and Polyois. These ingredients control the characteristics of the foam such as degree of rigidity / flexibility, density (foamed or solid) and cellular structure (open or closed. Two methods are used to make PU foams - (1) Chemical Blowing: - In this method, poiyol / isocynate reaction takes place inside a mould; in combination with water these produce a polyurea and carbondioxide (C02). The C03 serves as the blowing agent; the gas is released after cross linking takes place. (2) Physical Blowing: - In this method, the auxiliary blowing agent (trifluorochloromethane) evaporates during the reaction between polyois and polyisocyanate, and this produces a foaming action. In the open cell foams, the gas escapes during processing; in closed cell foams, the release of gases is largely retained and helps improve the foam's thermal insulation properties.
The foams and sponges made by the conventional manufacturing process usually have the following disadvantages:-
They do not have continuous porous structure.
Their elasticity does not remain as good in wet state.
They do not exhibit superior mechanical strength and also have less abrasion resistance. This gives them a short life.
The foams and sponges made by the conventional manufacturing process are not always resistant to organic chemicals and alkalis.
The present invention is a process of manufacture of a synthetic sponge called PVA Sponge, which is the only synthetic sponge essentially composed of Poly Vinyl Acetate which possesses a 3-Bimensional open cell structure similar to that of a natural sea sponge,
The present invention "Process of PVA Sponge" is designed with a goal to overcome the disadvantages of conventional methods of manufacture of sponges and to provide a superior quality sponge for various applications.
The first objective of this invention is to produce a sponge with a continuous porous structure so that each of its pores is not independent but interconnected,
The second objective of this invention is to produce a highly absorbent sponge material.
The third objective is to ensure that the elasticity of the sponge produced remains intact even in wet conditions.
The next objective is to give superior mechanical strength to the sponge,
Another objective is to produce a sponge that does not react with organic solvents and chemicals like alkalis, so as to give it an industrial application.
Also, the pore size and hardness should be easily controllable and so should be the colour of the sponge. This will also facilitate the absorbing of foreign matter or special abrasives during the manufacturing process.
The present invention "Process of PVA Sponge" will now be explained in detail with the help of the chemical equation.
PVA Sponge is the synthetic sponge essentially composed of poly vinyl acetate which posses a 3-dimensional open cell structure similar to that of a natural sea sponge. The PVA Sponge has a porous structure made from water soluble PVA acetalised with an acid catalyst (Sulphuric acid). During the acetalising process, the pore forming agent is added. After a water soluble porous structure is made, the agent is then extracted. The finished product has a complete 3-dimensionai structure, which is porous and continuously interconnected (i.e. Unicellular).
_|__CH2 _ CH __ CH2__ CH _]n__ + HCHO acid catalyst
| | " Sulphuric Acid (H2S04)
__L_CH2 _ CH__ CH2__ CH __ CH2_ CH]n_ + H20
0 CH2 0 OH
(A) Aqueous solution preparation; -
The solubility of PVA depends on the degree of polymerization and percent hydrolysis, which not only affects the hardness, affinity to water and strength of the sponge, but also to some extent the manufacturing process itself. The selection of proper grade of
PVA therefore requires some care.
Completely hydrolyzed grades of PVA are normally used. The maximum practical concentration for PVA emulsions prepared by using conventional high speed mixers are :-
Ultra high viscosity PVA 10-12%
High - viscosity PVA 15-20%
Low - viscosity _ 30-40%
PVA is charged into cold water and heated up to get its emulsion. Direct injection or indirect jacketed heating by steam is the heat source for dissolution. It is completed if the particles of PVA disappear into the aqueous solution. The following procedure is used:-
1) Add required amount of water at room temperature,
2) The charging speed of PVA should be as slow as possible, into the vertex of the water, so that added PVA wets out and disperses completely into the water,
3) Continue stirring for 10-15 minutes without raising the temperature immediately to avoid agglomeration.
4) Then heating should be started and when the slurry temperature reaches 97-98° C the PVA powder get completely dissolved.
5) Turn off the heat and cool. Continue stirring till the PVA emulsion comes to room temperature.
(B) Sponge Preparation :-
The following is a typical formulation that can be converted into a poly vinyl formal cellular product (PVA sponge),
PVA (polysizer 173) 104gms
Water 1155 cc
Acid (C.P.95%) 200 cc
Formaldehyde / paraformaldhyde 150 cc
Alkyl aryl polyoxymethylene 4gms
1) PVA emulsion is prepared by the above mentioned method and some additives like antioxidants and preservatives are added to the emulsion during the process itself.
2) Sulphuric acid is added to the PVA solution and the solution is cooled to room temperature.
3) Formaldehyde / Paraformalin and the wetting agent are added at the room temperature and the mixture is beaten with a high speed rotaiy mixer until it has attained maximum froth volume. Here the condensation reaction is initiated. At this initial stage of reaction, the reaction solution containing a large number of bubbles is poured into a mould.
4) During the reaction time of 8-10 hours at the room temperature or above, the degree of aeetalisation reaches 60-70% mole. Thus, the water soluble resin is converted into water insoluble sponge.
5) After the sponge is cured, it is washed thoroughly to remove the unreacted materials. The dried foams made by this method are low in density (0.03-0.09 gms / cm") and highly absorbent.
6) Inert fillers are added in the sponge at the mixing stage before frothing. The use of abrasive fillers will produce a sponge with an abrasive surface.
The above mentioned process generates the open cell PVA Sponge. Since this sponge is pure white in colour, colour can be added at any point. In fact, the sponge can also be dyed at the last stage.
The present invention "Process of PVA Sponge" has many advantages over the conventional manufacture of sponges and foams available in the market, some of these are mentioned below.
The present process can easily control the pore size and shape for a particular purpose and usage.
The PVA sponge produced by the present process has a complete, continuous and open cell structure and each of its pores are not independent but are interconnected., unlike the rubber sponge. This permits the sponge to be used as a filter element with high filtering efficiency and also enables it to be reused after cleaning.
The PVA sponge produced by the present process also has a remarkable property to absorb and retain water because of hydrophilic -OH radicals in the molecular structure and the capillary action caused by its fine pore structure. Thus this sponge can be used favorably for dehydrating, absorbing and painting applications.
The present process manufactures sponge with excellent wet state elasticity which makes it soft and flexible like natural sea sponge, when wet. Hence it can be used for cosmetic puffs, towels, bath sponges, mops and all household cleaning materials.
Since the present process uses PVA, the sponge produced by this process has superior mechanical strength, abrasion resistance and high resistance to organic solvents, acids and especially alkalis. Thus it can be used as an industrial element,
The present process produces PVA Sponge which is pure white, hence it can be easily coloured and also to a high degree of fastness.
The present process produces many different sizes and shapes of the PVA sponge are available as per applications. B: also allows us to control the hardness of the PVA Sponge.
Since by the present process, the pore size and shape of PVA sponge can be easily controlled, special types of abrasives or other foreign matter can be included and absorbed into the PVA sponge. It has a wide range of applications like household cleaning aids like mops, sponge blocks, sponge wash clothes, chamois etc. industrial cleaning aids like sponge rollers, sponge sheets, sponge wipes etc., industrial filters for air, water, oils, paints, varnishes and other chemicals, cosmetic puffs, etc.
I CLAIM :-
1) A Process of preparing three - dimensional open cell structured polyvinyl acetate
sponge comprising the following steps,
a) Preparing polyvinyl acetate emulsion by charging conventional high speed mixtures using water, and / or solvent under continuous stirring for a period of 10 to 15 minutes at a constant temperature;
b) Acetalistion of polyvinyl acetate emulsion obtained at step (a), added pore forming agent to make water soluble porous structure;
c) Frothing followed by washing;
2) The process as claimed in claim 1, where in PVA emulsion is prepared by charging conventional ultra high viscosity PVA 10-12% / high viscosity PVA 15-20% / low viscosity PVA 30-40% , into vertex of cold water and / or solvent and added additives^ preservatives, filler, under steam heating for a period of 10-15 minutes at constant temperature to foam a slurry.
3) A process as claimed in claim 2, wherein the temperature is raised up to 97-98 degree centigrade when slurry is completely dissolves, followed by constant stirring until PVA emulsion temperature comes down to room temperature.
4) A process as claimed in claims land 2, wherein the emulsion is prepared by using water and / or solvent used selected from, para formaldehyde in aqueous & Para formaline.
5) A process as claimed in claims 1 to 4, wherein the additive added is selected from alkyl aryl polyoxymethylene.
6) A process as claimed in claim 1, wherein the acetalisation of PVA carried out with formaldehyde using inorganic acid as a catalyst.
7) A process as claimed in claim 6, wherein the reaction is carried out over a period of 8-110 hours at room temperature and above, and acetalisation reaches upto 60-70%.
1) A process as claimed in claim L wherein the mixtures are added at room temperature and beaten with high speed rotary mixture until to attain maximum troth volume.
Dated this 14th Day of October 2003,
JOSEPH VARIKASEEY OF VARIKASERY & VARIKASERY
Agent for the applicant
|Indian Patent Application Number||493/MUM/2003|
|PG Journal Number||40/2008|
|Date of Filing||19-May-2003|
|Name of Patentee||MR. CHETAN RAVINDRA MEHTA|
|Applicant Address||701, SHLLPA APTS., JAGDUSHA NAGAR, GHATKOPAR (WEST), MUMBAI - 400 086.|
|PCT International Classification Number||C08F 118/08|
|PCT International Application Number||N/A|
|PCT International Filing date|