CN1727385A - Vulcanizing latex compounds without the use of metal oxide activators or a zinc based accelerator - Google Patents

Abstract

The present invention provides a latex compound comprising a natural rubber or a synthetic rubber material and an antioxidant comprising a zinc based synergist. The zinc based synergist may be selected from the group consisting of zinc 2-mercaptotoluimidazole and zinc 2-mercaptobenzimidazole, as well as combinations of these materials. The latex compounds may be cured without metal oxide, such as zinc oxide, and/or without zinc based accelerators. The invention further pertains to cured natural rubber or synthetic rubber material comprising the latex compounds, and curing systems and methods for curing the latex compounds without metal oxide and/or zinc based accelerators.

Description

Do not use metal oxide activators or zinc based accelerator vulcanizing latex compounds

Background of invention

Technical field

The present invention relates to not use metal oxide and/or zinc based accelerator to carry out the sulfurized latex compounds.Described latex compounds can comprise the zinc-base antioxidant material that zinc is provided to this mixture.The invention still further relates to and do not use metal oxide and/or zinc based accelerator to come the method for vulcanized latex film.

Background technology

Metal oxide such as zinc oxide can be used for vulcanizing latex compounds.Particularly, metal oxide is as the crosslinked donor of metal-chlorine in the activator of vulcanization system and the sovprene.For example, use zinc oxide as the crosslinked donor of the zinc-chlorine in the sovprene.Other metal oxide that can be used for vulcanizing latex compounds comprises magnesium oxide and plumbous oxide.

The proportion of zinc oxide is about 5.5, precipitation rapidly in water dispersion and latex compounds.Identical phenomenon also takes place in other metal oxide usually in water dispersion and latex compounds.Therefore, before each the use, need the container that contains such as the latex dispersions of the metal oxide of zinc oxide is carried out remix consumingly, because described metal oxide is precipitated to the bottom of this container usually.Simultaneously, when preparation contains promotor, oxidation inhibitor and during such as the latex dispersions masterbatch of the metal oxide of zinc oxide, needs frequent remix, promptly difficulty is time-consuming again.In addition, when splendid attire that adopts in to the industry of latex impregnation goods and steeping vat clean, can obviously observe the accumulation and the precipitation of metal oxide, for example under the situation of zinc oxide.Used latex compounds also can be found same phenomenon in bathing usually in the production of latex line.

Metal oxide, particularly zinc oxide play an important role to the activation of latex compounds.Therefore, need keep uniform concentration for latex material being carried out suitable sulfuration in described dispersion, yet partly owing to the proportion of described metal oxide, the level that accurately keep described metal oxide is very difficult, it is relevant especially with zinc oxide.

About another misgivings of zinc oxide are that zinc oxide level in natural rubber and the synthetic latex mixture is the major cause that dynamic and lasting viscosity rises, it has influenced the storage life of this class mixture.These misgivings exist equally to other metal oxide.Oxygen-free zinc (or other metal oxide) and zinc-base thiazole or dithiocar-bamate promotor, the fluctuation of the viscosity that then need not to worry again, and also natural rubber and synthetic latex mixture can be deposited for a long time.

Before the present invention, the function of zinc-base material is considered to only strengthen the performance of oxidation inhibitor, for example in the antioxidant systems that contains the zinc-base synergistic agent.In fact, in the prior art, 2-sulfydryl Vermox zinc (zinc 2-mercaptotoluimidazole) compound is considered to strengthen the high-temperature behavior of the mixture that contains thermoplastic polymer.

Herein, unless specifically stated otherwise, all umbers and per-cent are all based on weight.

Summary of the invention

The present invention relates to following unexpected discovery: need not to use metal oxide and/or zinc based accelerator effectively to vulcanize to latex compounds.In one aspect of the invention, described latex compounds comprises the zinc-base antioxidant material, and the antioxidant systems that contains the zinc-base synergistic agent of zinc for example is provided in described mixture.Described zinc-base synergistic agent plays multiple action in latex compounds; For example 1) antioxidant synergist, the 2) activator of the mixture of sulfidizing, and 3) as the crosslinked zinc source of zinc-chlorine in the sovprene.The mixture that does not comprise metal oxide and zinc based accelerator also has acceptable physical property.

The present invention also provides the method for the latex film that vulcanizes containing metal oxide compound not and/or zinc based accelerator.In one aspect of the invention, described method is usually directed to the latex film that contains zinc-base antioxidant material (for example synergistic agent) is heated.Described method generally includes the emulsion agent film that forms containing metal oxide compound not or zinc based accelerator, and the step that this film is heated, and described film for example contains the complexes membrane of zinc-base antioxidant material.

Detailed description of the invention

Latex compounds of the present invention does not comprise metal oxide, as zinc oxide, magnesium oxide, plumbous oxide or its mixture.Described latex compounds also can not comprise zinc based accelerator.In embodiments of the invention, described latex compounds comprises zinc-base antioxidant material (for example synergistic agent).The content of zinc-base antioxidant synergist material can be about 0.1 part of each hundred parts of rubber (hereinafter referred to as " phr ") or lower, to about 5.0phr or higher.In one aspect of the invention, described zinc-base antioxidant synergist material is as the activator of latex compounds vulcanization system.

In embodiments of the invention, described zinc-base antioxidant material comprises the synergistic agent that is selected from 2-sulfydryl Vermox zinc (ZMTI) and 2-mercaptobenzimidazole zinc (ZMBI) or its composition.Zinc-base antioxidant material used in the present invention can comprise the composition of phenolic antioxidant (phenol) and ZMTI.In described mixture, can use R.T.Vanderbilt Co.Inc. separately, Norwalk, Connecticut, phenolic antioxidant that the U.S. (" Vanderbilt ") sells and the mixture VANOX  SPL of ZMTI, or it is used in combination with independent phenolic antioxidant (as the VANOX  L from Vanderbilt) and 2-sulfydryl Vermox zinc (as the VANOX  ZMTI from Vanderbilt).

But described latex compounds comprises the natural of baking or synthetic rubber section bar material usually.Described latex compounds can comprise one or more materials, and this material is selected from natural rubber, polyisoprene, sovprene, vinyl cyanide, styrene butadiene, vulcanized butyl rubber or the like and combination thereof.Used isoprene material comprises KRATON  polymkeric substance, and the KRATON  IR-401 of the KRATON  Polymers Group of Companies of business office is for example arranged in the Texas ,Usa Houston.Also can use Neoprene sovprene from the DuPont Dow Elastomers of Delaware, USA Wilmington.Described zinc-base antioxidant synergist material constitutes the part of described elastomerics vulcanization system, and, for example strengthen physical property, high temperature resistant and anti-aging property, whiter and brighter color and the smell that reduces film for the object of handling through described latex compounds provides other favourable performance.

In embodiment of the present invention, described latex compounds comprises the liquid dithiocar-bamate that contains water-soluble alkali, and described water-soluble alkali is sodium salt, ammonium salt, triethylamine salt, piperidinium salt or the like for example.In preferred embodiments, the described liquid dithiocar-bamate that contains water-soluble alkali can be the mixture of NB sodium dibutyl dithiocarbamate (NaDTC) and mercaptobenzothiazole sodium (NaMBT).

Described latex compounds also can comprise the additional promoter material, for example includes but not limited to the thiocarbamide of trimethylammonium, diethyl, ethylene, phenylbenzene or the like.This thiocarbamide can be the dibutyl thiourea of buying with trade(brand)name THIATE  U from Vanderbilt, particularly 1, and the 3-dibutyl thiourea.

Described latex compounds also can comprise the additive of any amount.The example of the indefiniteness of this class additive is latex modified dose, thickening material, fire retardant, softening agent or the like.Available comprises sodium lauryl sulphate (from the DARVAN  WAQ of Vanderbilt) and Sulfated Witconol 2301 (from the DARVAN  SMO of Vanderbilt) for latex modified dose.The available fire retardant comprises weisspiessglanz, and the available thickening material comprises the sodium polyacrylate thickening material, for example from South Carolina, USA Simpsonville, and the Paragum-231 of Para-Chem.

Except that having overcome the shortcoming of in latex compounds, using zinc oxide and other metal oxide, also found other advantage.Usually in the practice of gloves and the industry of balloon dipping, adopt the scope that latex compounds is diluted to about 25%-35%.Doing like this is the amount of picking up in order to limit on the building mortion, and the viscosity rising in the control maturing process, particularly in natural rubber and the application of polyisoprene latex.By using the latex compounds of stable viscosity, mixture for example as herein described can use the latex compounds of greater concn in steeping vat.In coagulating bath, can use the condensing agent of lower concentration.To some application, also may eliminate described condensing agent fully.

The latex compounds of stable viscosity provides the condition selected for the manufacturer and has adjusted condensing agent and chance that latex compounds concentration is picked up (pick-up) to obtain the best among multiple thickness.It is favourable being applied in it in production of nipple or baby bottle nipples.Using such as the direct impregnation in the condom manufacture also is favourable.But direct production pathmaster is with, family expenses and tolerance gloves (as industrial gloves) and need not repeatedly to flood.Can produce the more latex line of large section size.Simultaneously, in some applications,, need from prescription, remove metal oxide and zinc based accelerator such as zinc oxide as in the production of nipple or baby nipple.

Metal oxide and the zinc based accelerator removed from latex compounds such as zinc oxide have environmental benefit.Heavy metal content in the waste water that the elimination of metal oxide and zinc based accelerator can reduction equipment be discharged, this equipment is used for latex compounds is made useful commodity.

The present invention relates to comprise the latex compounds of the antioxidant systems that contains the zinc-base material, it can not vulcanize under the condition such as the metal oxide of zinc oxide and/or zinc based accelerator.Described zinc-base material can be selected from ZMTI and ZMBI, and described oxidation inhibitor also can comprise phenolic antioxidant.The invention still further relates to sulfuration and do not contain method, comprise the steps: to form the latex compounds film that comprises the oxidation inhibitor that contains the zinc-base material such as the latex film of the metal oxide of zinc oxide and/or zinc based accelerator, and to this film heating for some time.In embodiments of the invention, described film can grow to about 1 hour in height heating to about 150 ℃ temperature, for example in about 90 °-150 ℃ heating about 5-45 minute down.The invention still further relates to the vulcanization system that is used for latex compounds, wherein the zinc-base antioxidant synergist provides zinc for this system and as activator, this system comprises that described antioxidant synergist is the system of ZMTI and/or ZMBI.

Embodiment 1-3

The synthetic polyisoprenes latex compounds that contains component shown in the table 1 according to method preparation well known in the art.All components shown in the table 1 is all represented with phr..Embodiment 2 is for comprising the comparative example of zinc oxide.The liquid dithiocar-bamate of using in the listed mixture in the table 1 (WB-7) is the mixture of NaDTC and NaMBT.What use among the embodiment 3 is the aqueous dispersion of 2-sulfydryl Vermox.Need to prove that in embodiment 1-3 and other embodiment of this specification sheets, zinc oxide and sulphur can be from each suppliers.Zinc oxide and sulphur are ubiquitous on the market, and the source of these materials and the function of described embodiment are irrelevant, yet, usually zinc oxide is available from the Zinc Corporation of America of pennsylvania, USA Monaca, and sulphur is usually available from the R.E.Carroll Inc. of New Jersey Trenton.

The film of being made by the mixture of embodiment 1-3 vulcanizes under the different condition shown in the table 2.Described cure conditions is for to carry out 30 minutes and to carry out 20 minutes at 120 ℃ at 100 ℃.Tensile strength, 300% modulus and unit elongation to the film after each sulfuration are tested, test is carried out according to ASTM Test Method D412-98a (2001) e1 " vulcanized rubber and thermoplastic elastomer tensile standard method of test ", and this paper is incorporated herein by reference its integral body.The result is as shown in table 2.

Table 1
					Component	Embodiment			Component supplier or trade(brand)name
1	2	3
			The polyisoprene latex	100		100	100	KRATON，IR-401
Sodium lauryl sulphate	0.25	0.25			0.25				DARVANWAQ
			Zinc oxide	---		0.5	---	Various
Sulphur	1.5	1.5			1.5				Various
			Phenols AO and ZMTI mixture	2		2	---	VANOXSPL
2-sulfydryl Vermox	---	---			1				VANOXMTI
			Phenolic antioxidant	---		---	1	VANOXL
Dibutyl thiourea	1	1			1				THIATEU
			Liquid dithiocar-bamate (WB-7)	1		1	1	Vanderbilt
Sulfation oleic acid methyl esters	0.5	0.5			0.5				DARVANSMO

Table 2
				Application testing	The result
Embodiment
			1		2	3
At 30 minutes film of 100 ℃ of sulfurations
				Tensile strength, MPa	28.2	28.2	15
300% modulus, MPa	1.3	1.3	1.2
				Unit elongation, %	1080	970	960
At 20 minutes film of 120 ℃ of sulfurations
				Tensile strength, MPa	24.5	26.8	18.5
300% modulus, MPa	1.2	1.4	1.2
				Unit elongation, %	990	950	930

Table 2 shows, as long as described zinc source (ZMTI) exists, uses or do not use zinc oxide or zinc based accelerator all can obtain satisfied physical property to the polyisoprene latex compounds.This point is implemented example 3 and has confirmed, it does not conform to ZMTI and physical property is poorer than embodiment 1.Surprisingly the zinc that is comprised only accounts for about 13% weight ratio of described ZMTI molecule.

Embodiment 4-8

The natural latex rubber mixture that contains component shown in the table 3 according to method preparation well known in the art.All components shown in the table 3 is all represented with phr..Embodiment 4 is for comprising the comparative example of zinc oxide.The liquid dithiocar-bamate of using in the listed mixture in the table 3 is WB-7, i.e. the mixture of NaDTC and NaMBT.

Make the film of about 25 mils of thickness (mil) by the mixture of embodiment 4-8 to about 40 mils.Described film was 100 ℃ of sulfurations 20 minutes, and the film of using subsequently after ASTM Test Method D412-98a (2001) e1 vulcanizes each carries out tensile strength, 300% modulus and unit elongation test.The result is as shown in table 4.

According to the test to described sulfide film, to not conforming to zinc source (embodiment 6) and not containing the sample of the dithiocar-bamate (embodiment 7) that is derived from liquid dithiocar-bamate, the raising of its physical property is slower.Therefore no longer embodiment 6 and 7 is tested and consider.

To sulfuration mixture (embodiment 4, the 5 and 8) mild heat of remainder, wore out 7 days at 70 ℃.Application ASTM Test Method D412-98a (2001) e1 carries out tensile strength, 300% modulus and unit elongation test to the sample of heat aging.

The test shows that the sample of heat aging is carried out, with aging before the test the carried out physical property of comparing described mixture improved.Therefore, at first described sample is carried out undervulcanization processing, because under the normal aging temperature, deterioration to a certain degree can take place but not continue crosslinked in the caoutchouc latex film properties of complete cure.

Described about 25 mils to the thick film of about 40 mils, are obtained residence time that suitable sulfided state needs to grow slightly, high slightly temperature or both combinations.The wall thickness of latex test gloves is about 10 mils usually, and wherein applied cure conditions must be suitably.Yet after the normal heating weathering process of described emgloves industrial application, none shows deterioration among the embodiment 4,5 or 6.Described test proves, can be under the condition of not using zinc oxide or zinc based accelerator (embodiment 5), the natural rubber mixture vulcanized obtain having the product that to accept physical property, and for natural rubber, described liquid dithiocar-bamate has than the more obvious effect of thiocarbamide (comparative example 7 and 8) crosslinked action.

Table 3
							Component	Embodiment					Component supplier
4	5	6	7	8
					NR LATZ	100		100	100	100	100	Getahindus(M)Sdn Bhd
Sodium lauryl sulphate	0.25	0.25	0.25	0.25			0.25						DARVANWAQ
					Zinc oxide	0.5		---	---	---	---	Various
Sulphur	1.5	1.5	1.5	1.5			1.5						Various
					Phenols AO and ZMTI mixture	2		2	---	2	2	VANOXSPL
Dibutyl thiourea	1	1	1	1			---						THIATEU
					Liquid dithiocar-bamate (WB-7)	1		1	1	---	1	Vanderbilt
Sulfation oleic acid methyl esters	0.5	0.5	0.5	0.5			0.5						DARVAXSMO

Table 4
						Application testing	The result
Embodiment
					4		5	6	7	8
100 ℃ of sulfurations 20 minutes
						Tensile strength, MPa	18.1	16.9	13.4	7	16.8
300% modulus, MPa	2	1.5	1.1	0.8	1.3
						Unit elongation, %	690	730	740	780	770
						Wore out 7 days at 70 ℃
Tensile strength, MPa	23.1	21.1			22.9
						300% modulus, MPa	2.6	2			1.7
Unit elongation, %	630	720			790

Embodiment 9-13

The sovprene latex compounds that contains component shown in the table 5 according to method preparation well known in the art.All components shown in the table 5 is all represented with phr..Embodiment 9 is for comprising the comparative example of zinc oxide.The mixture that will be used for embodiment 9-13 preparation from the sovprene Neoprene of DuPont Dow Elastomers.The liquid dithiocar-bamate of using in the listed mixture in the table 5 is WB-7, i.e. the mixture of NaDTC and NaMBT.Thickening material is the Paragum 231 from Para-Chem, and understands as those skilled in the art, and its add-on is for reaching the required amount of optimum viscosity of every kind of application (for example testing gloves, domestic purpose gloves, line, balloon, condom or the like).

The film of being made by the mixture of embodiment 9-13 vulcanizes under the different condition shown in the table 6.Described cure conditions is for to carry out 30 minutes and to carry out 45 minutes at 120 ℃ at 120 ℃.Using tensile strength, 300% modulus and the unit elongation of the film after ASTM Test Method D412-98a (2001) e1 vulcanizes each tests.After the test, with described at 30 minutes film of 120 ℃ of sulfurations 100 ℃ of heat agings 22 hours, and then use ASTM Test Method D412-98a (2001) e1 test tensile strength, 300% modulus and unit elongation.The result is as shown in table 6.

Table 5
							Component	Embodiment					Component supplier
9	10	11	12	13
					The sovprene latex	100		100	100	100	100	DuPont Dow
Sodium lauryl sulphate	0.25	0.25	0.25	0.25			0.25						DARVANWAQ
					Zinc oxide	5.0		---	---	---	---	Various
Sulphur	1.5	1.5	1.5	1.5			1.5						Various
					Phenols AO and ZMTI mixture	2		2	---	2	2	VANOXSPL
Dibutyl thiourea	1	1	1	1			---						THIATEU
					Liquid dithiocar-bamate (WB-7)	1		1	1	---	1	Vanderbilt
Sulfation oleic acid methyl esters	0.5	0.5	0.5	0.5			0.5						DARVAXSMO
					Thickening material	As required---→ table 5					Para-Chem

Table 6
						Application testing	The result
Embodiment
					9		10	11	12	13
120 ℃ of sulfurations 30 minutes
						Tensile strength, MPa	26	25.4	20.9	17.5	15.3
300% modulus, MPa	2	2	1.8	1.8	1.5
						Unit elongation, %	810	810	830	810	850
						120 ℃ of sulfurations 45 minutes
Tensile strength, MPa	29.3	29.3	22.3	25.5	21.9
						300% modulus, MPa	2	2	1.6	1.8	1.6
Unit elongation, %	790	790	840	800	860
120 ℃ of sulfurations 30 minutes, wore out 22 hours at 100 ℃ then
						Tensile strength, MPa	34	29.9	34.6	26.6	29.6
300% modulus, MPa	2.4	2	2.2	2.1	1.7
						Unit elongation, %	700	710	700	670	760

The test result of sovprene film is unexpected, realizes satisfied sulfuration because sovprene well known in the art depends on a large amount of metal oxides.For example, in embodiment 10, do not use zinc oxide or zinc based accelerator promptly to obtain good physical property.These results show that the ZMTI in the described antioxidant systems provides the zinc of capacity, except that set up sulfur-crosslinked, it is crosslinked also to set up zinc-chlorine.

The test result of the mixture of embodiment 11 shows, than the zinc oxide (embodiment 9) of 5.0phr the vulcanization rate and the vulcanized quality of sovprene film had bigger influence from the zinc of described ZMTI.The physical property result of the embodiment 10 of the oxygen-free zinc in fact test result with embodiment 9 is suitable.Yet the physical property test result of embodiment 11 that does not contain ZMTI is obviously lower.

Described result shows that also thiocarbamide accelerator system and liquid dithiocar-bamate WB-7 work in coordination with.To the sovprene latex, in mixture, use described thiocarbamide (embodiment 12) separately or in mixture, use described dithiocar-bamate (embodiment 13) to obtain medium result separately, and the mixture that comprises the embodiment 10 of described thiocarbamide and liquid dithiocar-bamate simultaneously produces good physical property in described sovprene latex film, it is the sign of the obtained synergy of the present invention, and promptly any independent promotor is all made up effectively not as both.

As mentioned above, with among the embodiment 9-13 at 30 minutes sample of 120 ℃ of sulfurations about 100 ℃ of heat agings 22 hours.The heat aging of sulfuration sovprene latex film tends to cause deterioration usually, shows as and continues crosslinked increase tensile strength and modulus, finally causes the hardening of sovprene latex film to become fragile.Yet (for example embodiment 10-13) shows tangible degradation without any heat aging sample of the present invention.Unique test characteristic that numerical value descends is a unit elongation.Compare with other mixture, the sovprene latex film of embodiment 10 has the increase minimum of tensile strength and modulus, and has kept its most original physical property behind heat aging.These aspects of described embodiment result are unexpected especially, overthrown the protection chloroprene polymer this general viewpoint of the big amount zinc oxide of thermal degradation when needs does not take place.The limited amount zinc that is provided by described synergistic agent must limit quantity crosslinked in the described polymkeric substance, thereby has kept primary characteristic and delayed sclerosis and the generation of embrittlement film.

Claims (20)

1. latex compounds, the oxidation inhibitor that comprises natural rubber or tartan and comprise the zinc-base synergistic agent, wherein said latex compounds is the containing metal oxide compound not.

2. latex compounds as claimed in claim 1, wherein said oxidation inhibitor comprise the zinc-base synergistic agent that is selected from 2-sulfydryl Vermox zinc and 2-mercaptobenzimidazole zinc.

3. latex compounds as claimed in claim 1, the amount of wherein said zinc-base synergistic agent are about 0.1 part to about 5.0 parts of each hundred parts of rubber.

4. latex compounds as claimed in claim 1, it does not contain zinc based accelerator.

5. latex compounds as claimed in claim 1, wherein said oxidation inhibitor also comprises phenolic antioxidant.

6. latex compounds as claimed in claim 1 also comprises liquid dithiocar-bamate.

7. latex compounds as claimed in claim 6, wherein said liquid dithiocar-bamate are the mixture of nabam and mercaptobenzothiazole sodium.

8. latex compounds as claimed in claim 1 also comprises thiocarbamide promotor.

9. latex compounds as claimed in claim 1, wherein said tartan is selected from polyisoprene, sovprene, vinyl cyanide, styrene butadiene, vulcanized butyl rubber and combination thereof.

10. by the described latex compounds of claim 1 being vulcanized sulfurized natural rubber or the tartan that obtains.

11. comprise manufacturing a product of described sulfurized natural rubber of claim 10 or tartan.

12. the method for sulfurized natural rubber or tartan, comprise the steps: that the latex compounds that will comprise natural rubber or tartan and comprise the oxidation inhibitor of zinc-base synergistic agent makes film, and the film that is formed by described latex compounds heated, wherein said latex compounds is the containing metal oxide compound not.

13. method as claimed in claim 12, wherein said oxidation inhibitor comprise the zinc-base synergistic agent that is selected from 2-sulfydryl Vermox zinc and 2-mercaptobenzimidazole zinc.

14. method as claimed in claim 12, wherein said latex compounds does not contain zinc based accelerator.

15. method as claimed in claim 12, wherein said tartan is selected from polyisoprene, sovprene, vinyl cyanide, styrene butadiene, vulcanized butyl rubber and combination thereof.

16. method as claimed in claim 12, wherein said latex compounds also comprises phenolic antioxidant.

17. method as claimed in claim 12, wherein said latex compounds also comprises liquid dithiocar-bamate.

18. method as claimed in claim 12, wherein said latex compounds also comprises thiocarbamide promotor.

19. be used for the vulcanization system of latex compounds, be included as the oxidation inhibitor that contains the zinc-base synergistic agent that described vulcanization system provides zinc, wherein said latex compounds is containing metal oxide compound and zinc based accelerator not.

20. vulcanization system as claimed in claim 19, wherein said zinc-base synergistic agent is selected from 2-sulfydryl Vermox zinc and 2-mercaptobenzimidazole zinc.