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This invention relates to a process for treating plasticized polyvinyl chloride for retarding the migration of the plasticizer without affecting any of the bulk properties of the polymer sheet.
Plasticized polyvinyl chloride (PPVC) is widely used for various applications and comprises a physical mixture of additives like plasticizer, various types of stabilizers, lubricants etc. Diethyl hexyl phthalate (DEHP) is being commonly used as plasticizer for polyvinyl chloride and it may contain 30 or more percentagge of the aame by weight. Because of heterogeous composition or by agint, DBHP may exude so that it may cause toxic effects. Several attempts have been reported by various researchers to minimise the leaching by grafting various polymerizable monomers of hydrophobic to hydrophilic in nature, by different techniques. However, it has been observed that other basic requirements like mechanical property, transperancy etc are significantly reduced on these modifications.
An object of this invention is to propose a process for treating plasticized polyvinyl chloride for retarding the migration of the plasticizer and without affecting any of the bulk properties.
Another object of this invention is to propose a process for treating plasticized polyvinyl chloride for retarding the migration of the plasticizer and without affecting he transparency.
According to this invention there is provided a process for treating plasticized polyvinyl chloride sheets for retarding the migration of the plasticizer comprising in the steps of immobilizing gelation auto cleaned sheets by gas discharge treatment.
In accordance with this invention PPVC sheets are cleaned by any known method, such as in a soap solution and then rinsed in distilled water and dried in a vacuum oven at a temperature of SO-GCC.
The cleaned dried sheet is gas discharge treated with a non depositing gas, such as nitrogen. Both sides of the sheets are separately subjected to a gas discharge treatment. Such a treatment is carried out for a period of upto 10 minutes/ and preferably upto a period of 5 minutes.
The cleaned sheet is then subjected to the step of gelatin immobilization. The step of gelatin immobilization consists in preparing a solution of gelating and heating to a temperature of 60-70*C
The immobilization is effected in the presence of a coupling agent, l-ethyl-3-(3-dimethyl amino propyl) carbodiimide, EDC with or without hydrochloride. The sheet is then dried, for example in a vacuum oven at 40-50°C .for 2-3 hours.
Further objects' and advantages of this invention will be more apparent from the ensuing example, and the discussion thereon.
EXAMPLE
Calendered PPVC sheet having a thickness of 0.3mm, is received from the division of polymer Technology of this Institute, a product of Penisula Polymers Pvt. Ltd., Trivandrum, India Sheet sizes of 50 X 50mm were cut and thoroughly cleaned with 0.5% soap solution and rinsed rigorously in distilled water thrice, and rinsed in Analar grade Methanol (Qualigens, India) and dried in a vacuum oven at 50-60°C.
Edward vacuum coating unit (E306A) was employed for the gas discharge treatment. The plasma reactor of such a unit consisted of a cylindrical dome of diameter 30 cm. The electrodes are in ring form positioned
at a height of 12 cm. from the base plate. A non-depositing gas, nitrogen was employed for the plasma glow generation at a pressure of 10 m bar.
The clean dried sheets were gas discharge treated for 2.5, 5.0, 7.5 and 10 minutes, both sides separately and exposed to 500 mg% solution of gelatin (S.D Fine Chemicals, India) for over-night at room temperature. Gelatin solution was prepared in deionised double distilled water by heating upto 60-70°C. Gelatin immobilization onto the gas discharge treated PPVC was also attempted in presence of a carboxylactivating agent, l-ethyl-3-(3-dimethyl amino propyl) carbodiimide, (EDC), hydrochloride (protein sequencing grade) (Sigma Chemicals Co., USA) with concentrations 100 mg, 250 mg, and 350 mg percentage respectively. The modified surface were kept in distilled water overnight to remove the loosely board gelatin. Then samples were dried in a vacuum oven at 40-50°C for 2hO hours.
Air and octane contact angles were measured on water equilbrated samples under distilled water with
the help of a Goniometer (Kernco Instruments Co., Inc. USA) to determine the polar and dispersion components of the surface energy of the modified and bare surfaces. Surface/^ energy parameters were calculated with the method of Andrade et al. Water contact angle was also noted for a relative comparison of bare, gas discharge treated and modified PPVC.
Migration of the plasticizer, DEHP in n-hexane was examined at 30°C. The modified and bare PPVC sheets of known area were treated with 20.0 ml of n-hexane. Exacting lOOuul of aliquots were withdrawn at intervals of 1,2,3,4 and 5 h. The solvent was evaporated completely and the residue dissolved in spectroscopic grade methanol. The absorbance was read at 274 nm using an ultra violet-visible region spectrophotometer where DEHP has the maximum characteristic. The amounts of DEHP migrated into the medium was quantitated from a calibration curve for DEHP in methanol.
Accelerated leaching studies were conducted at
70°C in polyethylene glycol {PEG-400) and cotton
J _ji „„^ -^«4-,^vmi nori h\7 hh«a loss of weiqht of the
samples at specific intervals. Samples of bare and modified sheets of known weight was immersed in 20.0 ml of respective medium and kept in air
oven at VCC. At intervals of 24,48,72 and 120 h, the samples were taken out, washed with 0.5% soap solution followed by thorough rinsing in distilled water. Then rinsed with methanol and dried at GCC. The dried samples were weighted and the percentage weight loss is then calculated.
The tensile strength and elongation of test samples were measured,, the ASTM standard test protocol by using a Chatillon Universal Test Stand Model UTSE 2. The sheets were cut in the form of standard dumb-bell shaped test specimens, having the length between the grips of 2.5 cm, width of 0.5 cm and a cross head speed of 1 inch per minute.
The transparency of the modified and bare sheets were checked by measuring the percentage transmission of light in the 700-350 nm region using a UV-Vis spectrophotometer.
Both the sides of the polymer sheets were exposed separately for 2.5, 5.0,7.5 and 10 mts. respectively.
It was observed that there was no significant reduction in leaching of DEHP upto a plasma treatment for 7.5 minutes. But, it was found the colour of the polymer becomes more yellowish due to degradation^ by abstraction of HCl. The exposure was optimized upto 5 mts. separately on each sides of the sheet.
The sessile drop water contact angle data(TABLE 1)
reflected the hydrophilic nature of GDT polymer surface
compared to the bare. It may be possible due to
the development of charged or polar groups onto PPVC
surface, while it is being glow discharge treated.
Previous studies bare shown that when a polymer
substrate was subjected to a non-polymerizing gas
plasma such as Ar, N2, H2 etc., the interaction of
ionised gas with the polymer causes the abstraction of H-atoms. Subsequent Reactions can lead lead to surface crosslinking or the attachment of atmospheric oxygen on exposure, thus increasing the surface polarity.
The gelatin immobilized PPVC in presence of 250 mg% carbodiimide, EDC showed least leaching compared to the other modified surface. There is a considerable reduction of leaching, approximately 69 and 53 percentage into PEG-400 and cotton seed oil respectively.
The carbondiimide, EDC act as a coupling agent which activates the carboxyl group of gelatin and can be bonded to the charged polymer surface, which is being created by gas discharge treatment. Tests were made to modify PPVC using carboxyl activated gelatin without GDT. It was .observed that this modified surface did not show any resistance to the migration of DEHP in comparision with the bare surface.
It was observed that 250 mg% EDC is an optimum concentration in terms of migration resistance. In the case of lesser or higher concentration, the amount of plasticizer loss is found to be more.
The stability of the gelatin bonded to the substrate was investigated by conducting accelerated leaching into PEG-400 and cotton seed oil at TCC after autoclaving the best modified surface. It was found that there was slight increase in plasticizer migration due to autoclaving effect, but there was considerable resistance compared to the bare one.
Table 3 shows the surface energy parameters of the bare and the best modified surface. It can be seen that the modified one is slightly hydrophilic in nature compared to the bare. Further, it is observed that the transparency and mechanical property of the PPVC are not much altered during this process of surface of modification (Table 3).
* I-GDT + overnight exposure to 500 mg% gelatin solution, II,III & IV - GDT + overnight exposure to same containing 100 mg, 250 mg, 350 mg% EDC
This invention relates to a process for treating plasticized polyvinyl chloride (PPVC) for retarding the migration of the plasticizer without affecting any of the bulk properties of the polymer sheet.
Plasticized polyvinyl chloride (PPVC) is widely used for various applications and comprises a physical mixture of additives like plasticizer, various types of stabilisers, lubricants? etc.. Diethyl hexyl phthalate (JDEHP) is being commonly used as plasti¬cizer for polyvinyl chloride and it may contain 30 or more percentage of the same by weight. Because of heterogenous compo¬sition or by aging, DEHP may exude so that it may cause toxic effects. Several attempts have been reported oy various researchers to minimise the leaching by grafting various poly-merisable monomers of hydrophobic to hydrophilic in nature, by different techniques. However, it has been observed that other basic requirements like mechanical property, transparency, etc. are significantly reduced on these modifications.
=^eference is invited to copending Application No. 1076/Cal/95 of 23.8.95 entitled 'A process for treating plasticized polyvinyl chloride (PPVC) for retaring the migration of the plasticizer'.
An object of this invention is to propose a process for treating plastitized polyvinyl chloride for retarding the migration of the plasticizer and without affecting any of the bulk properties.
Another object of this invention is to propose a process for
treating plasticized polyvinyl chloride for retaring the
migration of the plasticizer and without affecting the
transparency.
According to this invention? there is provided a process for treating plasticized polyvinyl chloride
In accordance with this invention, PPVC sheets are cleaned by any known method, such as in a soap solution and then rinsed in distilled water and dried in a vacuum oven at a temperature of
The cleaned dried sheet is gas discharqe treated with a non-
rlepositing gas, such as nitrogen. Both sides of the sheets are
separately subjected to a Qas discharqe treatment. Such a
sreatment is carried out for a period of upto 10 mins. and
ireferably upto a period of 5 mins..
he cleaned sheet is then subjected to the step of qelatin
(nmobil isat ion. The step of gelatin immobilisation consists in
reparing a solution of qelating and heating to a temperature of
ø C. The immobilisation is effected for a period of 3-24 hrs.i
referably overnight in the presence of 100-350 may, of a
Dupling agent* l-ethyl~3-(3-dimethyl amino propyl) carbodiimide,
DC with or without hydrochloride. The sheet is then dried, for
o 9. in a vacuum oven at 40-50 C for 2-3 hrs..
further objects and advantages of this invention will be more parent from the ensuing example and the discussion thereon.
EXAMPLE
Calendered FPVC sheet having a thickness of 0.3 mm is
received from the division of a polymer Technology of this
Institute, a product of Peninsula Polymers Pvt. Ltd., Trivandrum,
India Sheet sizes of 50x50 mm were cut and thoroughly cleaned with 0.5% soap solution and rinsed rigorously in distilled water
thrice, and rinsed in Analar grade Methanol CQualigens, India) and dried in a vacuum oven at 50-60^C. / ^
double distilled water by heating upto 60-70 C. Gelatin immobili¬sation ontc- the gas discharge treated PPVC was also attempted in
presence of a carboxyl activating agent, l-ethyl-3-C3-dimethyl
amino propyl) carbodiimide, (EDO, hydrochloride (protein sequen-
cing grade) CSigma Chemicals Co., USA) with concentrations lOOmg,
250mg, and 350mg percentage respectively. The modified surface
were kept' in distilled watsr overnight to remove tire loosely
■
board gelatin. Then samples were dried in a vacuum oven at 40-5C C for 2-3 hours.
Migration of the plasticizer,
examined at 30C The modified and bare PPVC sheets of known area
were treated with 20.0 ml of n-hexane. Exacting lOOuul of aliquots were withdrawn at intervals of 1,2,3,4 and 5h. The
solvent was evaporated completely and the residue dissolved in
spectroscopic grade methanol. The absorBance was read at 274 nm
using an ultra violet-visible region spectrophotometer where DEHP
has the masimun characteristic. The amounts of DEHP migrated into the medium was quantitated from a calibration curve for DEHP in
methanol.
washed with 0.5" soap solution followed by thorough rinsing in distilled water, then rinsed with methanol and dried at 60C. The
dried samples were weighed and the percentage weight loss is then
calculated.
The tensile strength and elongation of test samples were
measured, the ASTM standard test protocol by using a Chatillon
Universal Test Stand Model UTSE 2. The sheets were cut in the
.
form of standard dumb-bell shaped test specimens, having the
length between the grips of 2.5 cm, width of 0.5cm and a cross head speed of 1 inch per minute.
leaching of DEHP upto
due to degradation, by abstraction of HCl. The exposure was
optimized upto 5 mts. separately on each sides of the sheet.
/
The sessile drop water contact angle data CTable 1>
/ reflected the hydrophilic nature of GDT polymer Surface compared
to the bare. It may be possible due to the development of charged
or polar groups onto PPVC surface, while it is being glow discharge treated. Previous studies bare shown that when a
accompanying drawings.
Figs.l to 4 depicts the accelerated migration of DEHP into PEG-400 and cotton seed oil at 70 C from bare and mofified PPVC.
The gelatin immobilized PPVC in presence of 250 mg%
carbodi iinide, EDC showed least leachi.ng compared to the other
/ modified surface. There is a considerable reduction of leaching,
appromataly 69 and 53 percentage into PEG-400 and cotton seed o i 1 respec t i ve 1 y ( Fig. 122) ,
WE CLAIM!
1. A process for treating plasticized polyvinyl chloride (PPVC)
for retarding, the migration of the plasticizer, comprising in the
steps of
cleaning by a known method and drying the PPVC sheets, subjecting
them to a gas discharge treatment with a non-depositing gas for a
period of upto 10 mins. and thereafter to a step of gelatine
immobilisation by treating them with a gelatin solution in the
presence of a coupling agent such as herein describedf rinsing
and drying the sheets to obtain the treated PPVC sheets.
2. The process as claimed in claim 1 wherein said PPVC sheets are
cleaned by a known method, such as in a soap solution followed by
rinsing in distilled water and drying in a vacuum oven at 50-
o 60 C.
3. The process as claimed in claim 1 wherein the gas used in the gas discharge treatment is a non-depositing gas, such as nitrogen.
4. The process as claimed in claim 1 wherein said gas discharge treatment is carried out upto a period of 5 mins..
5. The process as claimed in claim 1 wherein both sides of the
sheet are separately subjected to a gas discharge treatment.
6. The process as claimed in claim 1 wherein the step of gelatine
immobilisation, a 500 mg*/. solution of gelatine is used.
7. The process as claimed in claim 6 wherein said solution of
gelatine is prepared in deionised double distilled water, by
heating upto 60-70 C.
8. The process as claimed in claim 1 wherein said step of
gelatine immobilisation is carried hut for 3 to 7A hrs..
9. The process as claimed in claim 1 wherein said step of
gelatine immobilisation is carried out overnight.
10. The process as claimed in claim 1 wherein said coupling
agent is 1-ethy1-3(3-dimethyl amino propyl) carbodiimide
hydrochloride.
11. The process as claimed in claim 1 wherein said coupling agent
is used in a concentration of 100 to 350 mg%
12. The process as claimed in claim 1 wherein said coupling agent
is used in a concentration of 250 mg%.
13. The process as claimed in claim 1 wherein after the step of
gelatine immobi 1 isation, said PPVC sheets are rinsed overnight in
o distilled water and dried in a vacuum over at 40-50 C for 2-3
hrs. .
14. A process for treating plasticised polyvinyl chloride
substantially as herein described. |