Low Protein Latex for Dipped Goods

Beng Thye, Lim., Swee Hua, Tan.

Abstracts

Studies by previous researchers showed that NR latex contains about 0.95% of rubber protein. They are of various molecular weights but the majority are in the range of 10-50KD, of which those of 14-30KD do cause allergenic reaction to some users.

This paper presents results from comparative study of EP (Extractable Protein) and AP (Antigenic Protein) of some commercial latex articles produced from normal latex concentrate and those produced from low protein latex.

The results showed that over the years, much improvement has been made by Malaysian Gloves Manufacturers in reducing EP in gloves. From commercial examination glove samples studied, results obtained show that 38% with EP <50ppm, 12% with EP between 51-100ppm and 50% with EP >200ppm but less than 400ppm. AP results of these gloves were split equally with 50% below 10ppm and 50% above 10ppm. Whereas gloves made from low protein latex gave EP of unleached gloves consistently below 100ppm and those leached consistently below 50ppm by both ASTM and RRIM modified Lowry method; AP by ASTM method are all below 5ppm.

One can conclude from these results that to ensure consistently low EP and AP in latex articles, the use of low protein latex as starting material is essential.

1. INTRODUCTION

Natural Rubber (NR) latex contains about 0.95% of rubber protein. These proteins are known to be present are as follows;

i). Rubber fraction - 27.2%

ii). Serum fraction - 47.5%

iii). Bottom fraction - 25.3%

Rubber protein are of various molecular weight but the majority in the range of 10 – 50kD. Studies show protein of 14 – 30kD does cause allergenic reaction to some users.

Studies by Dr. K. Turjanmaa and MRB has shown 60% of the hypersensitive persons have no allergic response to gloves with extractable protein below 400ppm and 100% of negative responses were observed at EP below 100ppm .

2. REMOVAL OF RUBBER PROTEIN

In the market today we can find various brands of gloves with low EP. Most of these gloves are either chlorinated or have undergone post washing / treatment to remove the EP. As such, the removal of these proteins in rubber articles will reduce significantly the risk of Type I Allergy.

Protein in NR can be removed either from wet latex stage or from dry rubber articles. Rubber protein in latex can be removed by the following methods;

i). Biological process - enzymatic digestion

ii). Chemical process - denaturing of protein

iii). Physical process - removal of protein i.e. centrifugation

Whereas protein in rubber articles can be removed by;

i). Multiple washing - leaching with water or enzyme in water

ii). Chlorination

iii). Polymer coating - Barrier

As we know clonal difference do not have significant variance in term of total available proteins. But our own studies have led us to postulate that clonal differences and seasonal changes do have effects on total water extractable proteins. This was evidenced from the wide range of EP of unleached film made from different batches of latex concentrate at different times of the year. Details in Table 1.

Table 1 : Unleached EP of Latices From Different Sources

Month / Year	Source A	Source B	Source C
March 1997	1530	-	-
October 1997	790	1213	866
January 1998	1234	-	-
February 1998	1072	1126	-
March 1998	1406	-	-
September 1999	687	-	-

* All latices were compounded into normal 2 parts compound and EP were tested with

RRIM-Modified Lowry Method.

This makes process control more difficult and thus affects the consistency of EP and AP in gloves from time to time.

3. LOW PROTEIN LATEX PROPERTIES - LOPROTEX LPX

Table 2 shows the typical colloidal properties of LOPROTEX LPX. These properties are closely resembling those of normal latex concentrates except for the much lower non-rubber content and higher MST.

Table 3 ( a ) shows protein contents of LOPROTEX LPX. The leached rubber products produced from this latex give excellent results in EP and AP of 50ppm and 3.5ppm maximum respectively.

Table 2 : LOPROTEX LPX Latex Colloidal Properties

PROPERTIES	LOPROTEX LPX	Normal Latex Concentrate
Total Solid Content (%)	60.20 – 61.20	61.20 – 62.00
Dry Rubber content (%)	60.00 min.	60.00 min.
Non-Rubber Solid (%)	0.20 max	2.00 max
Alkalinity (%)	0.35 max	0.30 max (LATZ) & 0.60 min (HA)
MST @ 55% TSC (sec.)	2500 ± 500	800 min.
Volatile Fatty Acid No.	0.03 max	0.03 max
KOH No.	0.35 max	0.70 max
Magnesium Content (ppm)	10 max	10 max
Coagulum Content (ppm)	100 max	100 max
B/F Viscosity, 2/60 at 26±2 °C (cps)	65 - 80	65 – 80
pH	9.50 – 11.00	9.50 – 11.00
Specific Gravity (g/ml)	0.94 – 0.95	0.94 – 0.95

Table 3 ( a ) : LOPROTEX LPX Protein Contents

	Unvulcanized	Vulcanized
Extractable Protein (ppm) -	25 max. (50 max.)*	50 max. (100max.)*
Antigenic Protein (ppm) -	1.5 max.	3.5 max.
Total Nitrogen Content (%) -	0.06 max.	-

* EP result without leaching processes.

Recommended leaching process is 1 minutes wet-gel and 1 minutes post-cure leaching.

Figure 1 shows Antigen Protein identified by Western Blot Assay using Rabbit Sera a ASTM AL. There is a distinct band at 45kDa and 24kDa whereas those of 14kDa and below are some what degraded giving a smear image. Total Protein using Lowry protein asssay gives Total Protein in the range of 1524 mg/ ml to 3303 mg/ ml. This represent about 10-15% of Total Protein in normal HA concentrate which was reported to be 16 000 mg/ ml to 26 000 mg/ ml. Further Protein analysis on heat cure cast film using ASTM D5712-99 for EP and ASTM D6499-00 for AP ( Antigenic Protein ) gave very low EP and AP as shown in table 3 ( b ).

FIGURE 1 – ANTIGEN PROTEIN IDENTIFIED BY WESTERN BLOT ASSAY USING

RABBIT SERA a ASTM AL.

1. MARKER

2. ASTM AL 100μg

3., 4., 5., 6., 7. & 8. LOPROTEX LPX

9. GIVUL LP2

10. GICOM 1014 (BASED ON LPX)

Table 3 ( b ) : Extractable and Antigenic Protein Content of Unvulcanised Heatcure Cast films.

Sample reference	Antigenic protein content		Extractable protein content
	mg/ dm²	mg/ g	mg/ dm²	mg/ g
LOPROTEX LPX 3	0.4	0.3	12	<DL
	0.4	0.4	15	12
LOPROTEX LPX 4	0.4	0.4	13	13
	0.4	0.3	14	13
LOPROTEX LPX 5	0.4	0.3	<DL	<DL
	0.3	<0.25	11	<DL
LOPROTEX LPX 6	0.4	0.3	12	11
	0.4	0.4	15	14
LOPROTEX LPX 7	0.4	0.3	12	11
	0.4	0.3	<DL	<DL

(Duplicate Determination)

4. COMPARATIVE STUDY OF EP AND AP OF COMMERCIALLY AVAILABLE

LATEX PRODUCTS AND SIMILAR ARTICLES MADE FROM LOPROTEX LPX

Commercial samples of examination gloves, surgical gloves, household gloves, balloons,

prophylactics, rubber threads, finger cots, catheters and soothers were collected for EP, AP

and Nitrogen study. Table 4, 5, 6 and 7 show details of these samples.

3 batches of Loprotex LPX, each compounded into 2 parts compound as well as prevulcanised

latex were used to produce similar latex articles for comparative studies with those of

commercial samples. Results obtained are as shown in Table 9.

These commercial samples, as well as articles made from Loprotex lattices were tested for

Tensile, Modulus and Elongation at Break. Results are shown in Table 10.

Table 4 : Sampling of Latex Products

With proper surface treatment

No surface

treatment

Unknown surface treatment

Examination Gloves

100% (50% PF; 50% PP)

Surgical Gloves

100% (22% PF; 78% PP)

Household Gloves

100%

Balloons

67%

33%

Prophylactics

50%

Rubber Threads

100%

Finger cots

67%

33%

Catheters

100%

Soothers

60%

40%

* PF - Powder free gloves either by online or offline treatments i.e. chlorination or polymer coat.

* PP - Pre-powder gloves.

Table 5 : ASTM EP and AP results of Commercial Examination, Surgical and Household

Gloves

	EP ppm – ASTM	AP ppm - ASTM
Powder Exam Gloves
Average	205	29.9
Maximum	346	56.9
Minimum	15	0.7

Powder Free Exam Glove
Average	31	3.0
Maximum	54	7.6
Minimum	14	0.5

Powder Surgical Gloves
Average	78.6	9.42
Maximum	164	39.4
Minimum	DL	0.5

Powder Free Surgical Gloves
Average	40	1.6
Maximum	66	2.4
Minimum	14	0.7

Household Gloves
Average	29.3	8.3
Maximum	56	22.8
Minimum	14	1.0

Table 6 : Average EP of Various Commercial Latex Products Available In The Market

EP < 50

EP 51 - 100

EP 101 – 200

EP > 200

Avg. EP

Examination Gloves

RRIM Md. Low (ppm)

50%

21.3

50%

275.8

ASTM (ppm)

37%

17.3

13%

53.5

50%

292.1

Surgical Gloves

RRIM Md. Low (ppm)

56%

31.6

33%

142.3

11%

247

ASTM (ppm)

33%

16.3

22%

60.5

45%

136.3

Household Gloves

RRIM Md. Low (ppm)

67%

20.5

33%

ASTM (ppm)

67%

11.5

33%

56.2

Balloons

RRIM Md. Low (ppm)

67%

37.5

33%

1687

ASTM (ppm)

67%

26.9

33%

441.1

Prophylactics

RRIM Md. Low (ppm)

67%

33%

57.5

ASTM (ppm)

83%

17%

78.3

Rubber Thread

RRIM Md. Low (ppm)

11%

22%

77.5

22%

162.5

45%

393

ASTM (ppm)

11%

31.4

22%

87.1

33%

149.6

34%

287.3

Finger cots

RRIM Md. Low (ppm)

100%

18.3

ASTM (ppm)

100%

12.4

Catheters

RRIM Md. Low (ppm)

100%

17.8

ASTM (ppm)

100%

34.7

Soothers

RRIM Md. Low (ppm)

100%

ASTM (ppm)

80%

20%

70.7

Table 7 : Average AP of Various Commercial Latex Products Available in the Market

	< 2.5 ppm		2.6 - 5.0 ppm		5.1 - 7.5 ppm		7 .6 - 10 ppm		> 10 ppm
	%	avg.	%	Avg.	%	avg.	%	avg.	%	avg.
Examination Gloves	37%	0.7	0	-	0	-	13%	7.6	50%	33.4
Surgical Gloves	56%	1.2	11%	4.9	0%	-	0%	-	33%	28.6
Household Gloves	67%	1	0%	-	0%	-	0%	-	33%	22.7
Balloons	67%	2.3	0%	-	0%	-	0%	-	33%	12.1
Prophylactics	50%	1.4	17%	4.2	0%	-	0%	-	33%	18.3
Rubber Threads	33%	1.7	45%	3.6	11%	6	0%	-	11%	10.3
Finger cots	100%	0.6	0%	-	0%	-	0%	-	0%	-
Catheters	100%	1.1	0%	-	0%	-	0%	-	0%	-
Soothers	60%	0.8	0%	-	0%	-	20%	8.8	20%	14.8

Table 8 : Average Total Nitrogen of Various Commercial Latex Products Available In The

Market

	< 0.11 %		0.11 - 0.20 %		0.21 - 0.30 %		> 0.30 %
	%	Avg.	%	Avg.	%	Avg.	%	Avg.
Examination Gloves	0%	-	12%	0.20	75%	0.26	13%	0.33
Surgical Gloves	0%	-	16%	0.15	67%	0.26	17%	0.32
Household Gloves	0%	-	100%	0.15	0%	-	0%	-
Balloons	0%	-	33%	0.19	33%	0.26	34%	0.43
Prophylactics	83%	0.08	17%	0.12	0%	-	0%	-
Rubber Threads	0%	-	89%	0.18	11%	0.21	0%	-
Finger cots	33%	0.09	67%	0.12	0%	-	0%	-
Catheters	0%	-	50%	0.19	50%	0.25	0%	-
Soothers	40%	0.05	40%	0.18	20%	0.21	0%	-

Table 9 : Average EP, AP and TN of LOPROTEX LPX in Various Latex Products
		LOPROTEX LPX 2 parts compound		LOPROTEX LPX pre-vulcanized
		Unleached	Leached	Unleached	Leached
	Examination Gloves
	RRIM - EP (ppm)	37	28	81	37
	ASTM - EP (ppm)	-	19	-	38
	ASTM - AP (ppm)	-	0.7	-	2.2
	Total Nitrogen (%)	-	0.15	-	0.12
	Surgical Gloves
	RRIM - EP (ppm)	55	21	87	36
	ASTM - EP (ppm)	-	<DL	-	26
	ASTM - AP (ppm)	-	0.8	-	2.2
	Total Nitrogen (%)	-	0.12	-	0.14
	Household Gloves
	RRIM - EP (ppm)	43	28	84	74
	ASTM - EP (ppm)	-	67	-	49
	ASTM - AP (ppm)	-	1.5	-	5.8
	Total Nitrogen (%)	-	0.28	-	0.28
	Balloons
	RRIM - EP (ppm)	88	77 ( 25 )	83	114 ( 18 )
	ASTM - EP (ppm)	-	19	-	11
	ASTM - AP (ppm)	-	1.9	-	3
	Total Nitrogen (%)	-	0.34	-	0.42
	Prophylactics
	RRIM - EP (ppm)	10 ( 13 )	26 ( 13 )	20	9
	ASTM - EP (ppm)	-	12	-	12
	ASTM - AP (ppm)	-	0.6	-	0.5
	Total Nitrogen (%)	-	0.07	-	0.07
	Rubber Thread
	RRIM - EP (ppm)	52	16 ( 26 )	-	-
	ASTM - EP (ppm)	-	45	-	-
	ASTM - AP (ppm)	-	1.4	-	-
	Total Nitrogen (%)	-	0.15	-	-
	Finger cots
	RRIM - EP (ppm)	79	15	68	12
	ASTM - EP (ppm)	-	19	-	<DL
	ASTM - AP (ppm)	-	0.6	-	0.7
	Total Nitrogen (%)	-	0.09	-	0.07
	Catheters
	RRIM - EP (ppm)	17	11	18	8
	ASTM - EP (ppm)	-	<DL	-	<DL
	ASTM - AP (ppm)	-	0.6	-	1.1
	Total Nitrogen (%)	-	0.14	-	0.14
	Soothers
	RRIM - EP (ppm)	37	33	19	20
	ASTM - EP (ppm)	-	25	-	25
	ASTM - AP (ppm)		0.7	-	2
	Total Nitrogen (%)	-	0.13	-	0.09

* <DL - below detectable limit means < 10 mg/ g.

* ( ) - repeat result

Table 10 : Physical Properties Of Commercially Available Latex Products In Comparison

With Those Of Loprotex LPX Products

Description:		M 300 ( MPa)	M 500 ( MPa)	M 700 ( MPa)	Tensile ( MPa)	EB ( % )
1.) SURGICAL GLOVE
a.) Commercial Surgical Glove ( Powder )	Un:	1.2 - 1.8	2.5 - 4.4	10.9 - 20.6	24.1 - 31.6	751 - 866
	Age:	1.2 - 1.7	2.2 - 3.8	8.1 - 16.9	18.4 - 29.9	716 - 926
b.) Loprotex LPX Surgical Glove ( Powder )	Un:	0.9 - 1.2	1.5 - 2.4	5.9 - 12.4	24.6 - 28.6	858 - 965
	Age:	0.7 - 1.1	1.1 - 1.9	2.9 - 8.2	20.5 - 24.4	856 - 1052
c.) Commercial Surgical Glove ( Powder Free )	Un:	1.3 - 1.4	2.4 - 2.6	10.5 - 11.8	28.8 - 31.4	888 - 890
	Age:	0.9 - 1.1	1.8 - 4.1	3.3 - 5.9	18.9 - 24.7	966 - 1013

Description:		M 300 ( MPa)	M 500 ( MPa)	M 700 ( MPa)	Tensile ( MPa)	EB ( % )
2.) EXAM GLOVE
a.) Commercial Exam Glove ( Powder )	Un:	1.0 - 1.9	1.8 - 4.6	7.7 - 22.8	19.8 - 38.7	742 - 893
	Age:	0.9 - 1.9	1.5 - 4.3	4.3 - 22.2	13.7 - 34.9	712 - 969
b.) Loprotex LPX Exam Glove ( Powder )	Un:	0.9 - 1.2	1.4 - 2.9	5.5 - 15.0	23.2 - 27.7	821 - 973
	Age:	0.7 - 1.1	1.0 - 2.2	2.7 - 10.8	19.3 - 24.7	826 - 1050
c.) Commercial Exam Glove ( Powder Free )	Un:	1.3 - 1.9	3.2 - 4.5	10.9 - 20.6	16.0 - 29.7	727 - 870
	Age:	0.7 - 1.6	1.2 - 4.5	2.2 - 16.0	2.0 - 26.6	653 - 850

Description:		M 300 ( MPa)	M 500 ( MPa)	M 700 ( MPa)	Tensile ( MPa)	EB ( % )
3.) HOUSEHOLD GLOVE
a.) Commercial Exam Glove ( Powder )	Un:	2.6 - 3.0	7.2 - 8.6	20.8 - 22.1	20.8 - 25.8	673 - 754
	Age:	2.0 - 2.3	5.4 - 9.3	10.7 - 16.1	14.1 - 20.4	779 - 783
b.) Loprotex LPX Exam Glove ( Powder )	Un:	1.0 - 1.7	1.5 - 3.9	5.6 - 21.2	21.3 - 34.6	759 - 1023
	Age:	0.8 - 1.6	1.2 - 3.3	3.3 - 17.7	18.1 - 29.7	731 - 1116

Description:		M 300 ( MPa)	M 500 ( MPa)	M 700 ( MPa)	Tensile ( MPa)	EB ( % )
4.) FINGER COT
a.) Commercial Finger Cot ( Powder )	Un:	1.0 - 1.3	3.1 - 3.4	15.0 - 15.2	26.0 - 31.6	792 - 860
	Age:	1.3 - 1.4	2.5 - 2.6	9.4 - 9.7	22.0 - 27.3	884 - 918
b.) Loprotex LPX Finger Cot ( Powder )	Un:	0.8 - 1.5	1.4 - 3.7	5.3 - 23.2	18.7 - 31.4	739 - 932
	Age:	0.7 - 1.7	1.0 - 3.3	3.4 - 23.6	18.3 - 29.9	745 - 987
Description:		M 300 ( MPa)	M 500 ( MPa)	M 700 ( MPa)	Tensile ( MPa)	EB ( % )
5.) BALLOON
a.) Commercial Balloon	Un:	1.0 - 1.2	2.1 - 3.3	9.2 - 15.4	19.3 - 33.0	851 - 910
	Age:	1.0 - 1.3	1.7 - 2.4	4.0 - 7.7	22.6 - 26.5	935 - 1044
b.) Loprotex LPX Balloon	Un:	0.6 - 1.0	1.0 - 2.4	3.2 - 11.7	17.1 - 27.1	862 - 1055
	Age:	0.5 - 0.9	0.8 - 1.6	1.9 - 7.3	18.0 - 26.1	892 - 1147

Description:		M 300 ( N)	M 500 ( N)	Force@ Break ( N )	EB ( % )
6.) CATHETER
a.) Commercial Catheter	Un:	28 - 50	69 - 135	125 - 231	580 - 620
	Age:	21 - 45

Beng Thye, Lim., Swee Hua, Tan.

Abstracts

Natural Rubber (NR) latex contains about 0.95% of rubber protein. These proteins are known to be present are as follows;

Rubber protein are of various molecular weight but the majority in the range of 10 – 50kD. Studies show protein of 14 – 30kD does cause allergenic reaction to some users.

Studies by Dr. K. Turjanmaa and MRB has shown 60% of the hypersensitive persons have no allergic response to gloves with extractable protein below 400ppm and 100% of negative responses were observed at EP below 100ppm .

2. REMOVAL OF RUBBER PROTEIN

In the market today we can find various brands of gloves with low EP. Most of these gloves are either chlorinated or have undergone post washing / treatment to remove the EP. As such, the removal of these proteins in rubber articles will reduce significantly the risk of Type I Allergy.

Protein in NR can be removed either from wet latex stage or from dry rubber articles. Rubber protein in latex can be removed by the following methods;

Whereas protein in rubber articles can be removed by;

Month / Year

Source A

Source B

Source C

March 1997

1530

-

-

October 1997

790

1213

866

January 1998

1234

-

-

February 1998

1072

1126

-

March 1998

1406

-

-

September 1999

687

-

-

* All latices were compounded into normal 2 parts compound and EP were tested with

RRIM-Modified Lowry Method.

This makes process control more difficult and thus affects the consistency of EP and AP in gloves from time to time.

Table 2 : LOPROTEX LPX Latex Colloidal Properties

Table 3 ( a ) : LOPROTEX LPX Protein Contents

Vulcanized