Plastic pipes and fittings for home and industrial use

Abstract

Plastic pipes, fittings and other piping appurtenances prepared from CPVC formulations meeting requirements of ASTM-D 1784, cell class 23448-B, yet exhibiting suitable processability.

Description

BACKGROUND OF THE INVENTION

[0002] The invention relates to pipes, fittings and other piping appurtenances prepared from unique CPVC formulations. These formulations provide an improved combination of physical properties including heat deflection temperature, impact strength, tensile strength and modulus of elasticity. More particularly, the formulations meet requirements of ASTM-D 1784, cell class 23448-B, while maintaining suitable processability.

FIELD OF THE INVENTION

[0003] Plastic-type pipes, fittings and other piping appurtenances are an attractive alternative to those made of metal. One type is prepared from rigid poly(vinyl chloride) (PVC) formulations, and another is prepared from rigid chlorinated poly(vinyl chloride) (CPVC) formulations. These formulations are usually intended for use in an extruded or molded form.

[0004] CPVC is known to have excellent high temperature performance characteristics, among other desirable physical properties. Typically, commercial CPVC has an excess of about 57 percent by weight of bound chlorine, and is most conveniently made by the chlorination of poly(vinyl chloride) (PVC). See U.S. Pat. Nos. 2,996,489; 3,100,762; 3,334,077; 3,334,078; 3,506,637; 3,534,013; 3,591,571; 4,049,517; 4,350,798; 4,377,459; 4,412,898; and 4,459,387.

[0005] CPVC has become an important specialty polymer due to its relatively low cost, high glass transition temperature, high heat distortion temperature, outstanding flame and smoke properties and chemical inertness. The glass transition temperature of CPVC generally increases as the amount of chlorine increases. However, it is well known that CPVC resins have low impact properties. Also, as the chlorine content increases, the CPVC resin becomes more difficult to melt process, and becomes more brittle.

[0006] The increasing demand for CPVC pipes, vessels, valve bodies and fittings, and the fact that an impact-deficient CPVC matrix can be improved by compounding and blending it with other polymers, has provided significant incentive to develop better impact modified CPVC formulations having increased heat distortion temperatures, and increased ease of melt-processing. Most of these efforts have been directed toward rigid CPVC applications where acceptable impact strength and dimensional stability under heat are critical. These include the manufacture of exterior structural products, rigid panels, pipes and conduits, injection-molded and thermoformed industrial parts, appliance housings, and various types of containers, both large and small. Examples include those formulations of U.S. Pat. Nos. 3,264,375; 3,882,192; 3,886,235; 3,991,009; 4,105,711; 4,173,598; 4,362,845; 4,399,093; 4,443,585; 4,504,623; 4,504,624; 4,617,329; 4,663,375; 4,680,343; 4,766,177; 4,769,901; 4,786,350; 4,787,135; and 5,268,424.

[0007] For piping applications, ASTM-D 1784 sets forth the standard specifications for rigid CPVC formulations. They are identified in terms of cell classifications indicative of certain physical properties of the formulations. Cell class 23447-B is indicative of certain current commercially available CPVC formulations. The first digit (2) identifies the base resin as CPVC. The second (3) and third (4) digits identify impact strength and tensile strength characteristics, respectively. And the fourth (4) and fifth (7) digits identify modulus of elasticity and deflection temperature characteristics, respectively. The suffix designation (B) is indicative of a formulation's chemical resistance. Thus, those current commercial formations have the following properties according to ASTM-D 1784.

	Property and Unit	Cell Limit
2	Base resin	CPVC
3	Impact strength (Izod)
	J/m of notch	80.1
	ft.lb/in of notch	1.5
4	Tensile strength
	MPa	48.3
	Psi	7,000
4	Modulus of elasticity in tension
	MPa	2482
	Psi	360,000
7	Deflection temperature under load
	° C.	100
	° F.	212
B	Acid weight gain (%)
	(93d % H2SO4, 14 days, 55° C.)	5.0

[0008] It is desirable to increase heat deflection temperatures of CPVC formulations to levels higher than those provided by compositions of cell class 23447-B, i.e., to levels higher than 212° F. (100° F.). Doing so, however, result in a general degradation of one or more of those other physical properties characteristics of 23447-B formulations. For example, simply increasing chlorine content degrades impact strength levels below those mandated by ASTM-D 1784, cell class 23447-B. Adding or changing impact modifiers to compensate can degrade tensile strength and modulus of elasticity.

[0009] Even if those other cell class 23447-B properties are maintained at allowable levels, processability of the CPVC composition must also be maintained. An effective formulation for fluid handling applications must be moldable or extrudable. That is, a formulation can not degrade when processed in the manner required for extrusion or molding.

[0010] It is the object of the invention, therefore, to provide a moldable or extrudable CPVC formulation having a deflection temperature in excess of 212° F. (100° F.) while maintaining impact strength, tensile strength and modulus of elasticity at the same levels required of a cell class 23447-B formulation.

SUMMARY OF THE INVENTION

[0011] The invention provides pipes, fittings and other piping appurtenances, prepared from a moldable or extrudable CPVC formulation having a deflection temperature higher than 100° C. (212° F.). The formulations exhibit suitable processability, and meet requirements of ASTM-D 1784, cell class 23448-B. That is, the formulations have a deflection temperature of at least 110° C. (230° F.) yet maintain most, and in some cases all the other properties of a cell class 23447-B formulation.

[0012] Another aspect of the invention relates to pipes, fittings and other piping appurtenances prepared from such formulations which also meet the requirements of ASTM-D 2846 for home water handling and ASTM-F 438 and F 439 for industrial fittings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0013] Plastic pipes, fittings and other piping appurtenances according to the invention are prepared from CPVC formulations which meet the requirements of ASTM D 1784, cell class 23448-B. Such formulations have as their primary component a CPVC resin having a specified weight percent of chlorine of at least about 70%, and up to about 73%, preferably about 70 to 72%.

[0014] Suitable CPVC resins are resins having an inherent viscosity of about 0.60 to about 1.0, preferably about 0.65 to about 0.72. Such resins should also have a fused density of about 1.59 to about 1.68, preferably about 1.60 to about 1.67. Examples of such CPVC resins include TempRite 677×670, TempRite 657×612 and TempRite 677×705, available from Noveon, Inc. When the term inherent viscosity (IV) is used to describe the CPVC resins as above, technically it is the IV of the PVC resin used to make the CPVC. IV is not usually measured on the CPVC resin after the PVC has been further chlorinated to make CPVC resin. IV is defined in ASTM D-1243 as the ratio of the natural logarithm of the relative viscosity of a resin and the concentration of the solution used to measure the viscosity. ASTM D-1243 as measured herein on the PVC resin used to make the CPVC resin employs a 0.2 gram sample of PVC resin in 10 ml of cyclohexanone at 30° C. IV is a measurement of molecular weight and relates to K-value and degree of polymerization. The IV in this invention was determined using ASTM D-1243 on the PVC resin before it was chlorinated to make CPVC resin.

[0015] CPVC is known to the art and to the literature and is commercially available. CPVC can be made by any commercial chlorination process or the like, such as by a solution process, a fluidized bed process, water slurry process, thermal process, or a liquid chlorine process. The only limitation is that care must be taken to select those resins, or use those processes to prepare the resins, which will provide CPVC resins with the chlorine content, density and viscosity characteristics described above.

[0016] In theory, a CPVC resin used according to the invention may be blended with or contain generally small amounts of PVC and/or PVC copolymers. The amount of PVC homopolymer or copolymer could range from about 1% to about 50%. However, it is preferred that no amount of PVC homopolymer or copolymer be contained in the CPVC formulations according to the invention.

[0017] It is also possible that CPVC can be blended with another CPVC polymer. In those instances, the CPVC resin can be blended with another CPVC resin in an amount of other resin of about 1% to about 50%. Again, however, no amount should be added which would affect properties of the resin such as chlorine content which are necessary to obtain a formulation meeting the requirements of cell class 23448-B. It is preferred that a blend of CPVC resins not be used.

[0018] The CPVC formulations according to the invention should contain an impact modifier selected such that the tensile strength and modulus of elasticity will not be degraded below those levels required of cell class 23448-B formulations. Likewise, the formulation should exhibit suitable processability.

[0019] Since impact modifiers will tend to degrade other properties of the cell class (tensile strength and modulus), care must be used in their selection. As used herein, therefore, useful impact modifiers are only those which will not degrade cell class properties below the limits of ASTM-D 1784, cell class 23448-B, or processability. Such suitable impact modifiers include higher rubber (butadiene) content and high efficiency methylmethacrylate-butadiene-styrene (MBS) impact modifiers such as those sold under the name Kaneka B-22 and B-56 by Kaneka-America. Other MBS impact modifiers, as well as acrylonitrile-butadiene-styrene (ABS) impact modifiers, could be useful so long as cell class and processability is maintained. Examples include those sold under the names Metablen C-224 by Atochem, Acryloid KM-680 or BTA-751 by Rohm & Haas, or Blendex 310 or 338 by General Electric. It is not necessary for formulations according to the invention to contain any polyorganosiloxane-containing impact modifier. Suitable impact modifiers can be used in an amount of about 3 to about 15 phr, preferably about 5 to about 10 phr.

[0020] CPVC formulations according to the invention are extrudable or moldable, i.e., they exhibit “suitable processability”. Formulations according to the invention which exhibit suitable processability are those CPVC formulations which exhibit a melt flow index of at least about 1.0, preferably at least about 5.0 grams/10 minutes, and a dynamic thermal stability (DTS) time of at least about 1.0 minute, preferably at least 3.0 minutes at 235° C/35 r/min. Most preferred CPVC formulations according to the invention which exhibit suitable processability would have a melt flow index of at least about 1.0 gm/10 minutes, and even up to about 25 gm/10 min, or more, and/or a DTS time of at least 5 minutes, even more preferably at least 7 minutes at 235° C./35 r/min.

[0021] Melt flow rate is a standard measure of the rate of extrusion of molten resins through a die of a specified length and diameter under prescribed conditions of temperature, load and piston position in the barrel as the timed measurement is being made. See ASTM-D 1238. As used herein, the flow rate is expressed in terms of grams/i 0 minutes. The melt flow index for standard CPVC is normally measured at 215° C. for standard CPVC formulations, and is measured at 235° C. for the higher heat CPVC formulations according to the invention. In both cases, the standard load is 21,600 grams. Either method A (manual) or method B (automatic) as specified in ASTM-D 1238 can be used.

[0022] Dynamic thermal stability (DTS) is also a measure of processability. The DTS test is designed to measure the time-torque relationship of a particular formulation at selected temperatures using an instrument such as the Brabender Plasti-corder. See ASTM-D 2538. The test value generally reported, and used for comparison, is the “DTS time”. Unless specified otherwise, DTS time is defined herein as the time at a particular temperature/rotor speed, herein 235° C./35 r/min, required for the instrument torque to fall to is minimum value, with the polymer compound in the melted state, before beginning to increase, presumably due to instability and usually accompanied by autogenous cross-linking. As noted above, formulations according to the invention exhibit DTS time of at least 1.0, preferably 3.0 minutes under such conditions.

[0023] Other components may be present in formulations of the present invention. These include, for example, antioxidants, lubricants, stabilizers, impact modifiers, tinting colorants, blueing agents, pigments, Tg enhancing additives and processing aids, all of which serve various purposes known in the PVC compounding art. But no additive should be used which alters the unique combination of physical properties and processability associated with formulations according to the invention. For example, no additive should be used which degrades impact strength below those levels characteristic of cell class 23448-B. Likewise, no impact modifier should be used which degrades tensile strength and modulus of elasticity below the levels of that cell class. Nor should any additive be used which reduces processability below suitable levels.

[0024] Exemplary lubricants are polyglycerols of di- and trioleates, polyethylene, oxidized polyethylene, and high molecular weight paraffin waxes and mixtures thereof. Specific examples are oxidized polyethylenes such as those sold under the trade name AC 629 by Allied Signal, the paraffin waxes, such as those sold under the trade name Hostalube 165 by Hoechst Celanese. Lubricants can be used in an amount of about 0.01 to 5, preferably about 0.4 to about 2.0 parts per hundred resin (phr). Specific lubricants and their commercial sources are available by reference to Chemical Week-Buyers Guide.

[0025] Suitable heat stabilizing ingredients include phosphate stabilizers such as disodium phosphate, maleimides, sulfur compounds and alkyltin compounds. Tin compounds include methyltin, octyltin, mixed metal alkyltins, dialkyl tin dicarboxylates, methyl tin mercaptides, butyltin mercaptides, dialkyl tin bis(alkyl mercaptocarboxylate) including di-n-octyltin-S,S′-bis (isoctyl mercaptoacetate), butyl thiostannoic acid, and other ester tins. Di-C4-C8 alkyl tin stabilizers such as C4 to C8 alkyl tin carboxylates are preferred. A particularly preferred stabilizer is a tin thioglycolate such as that sold under the trade name Mark 292-S by Witco Chemical. Use levels can be in the range of about 1 to about 5.0, preferably about 2.0 to about 4.0, phr.

[0026] Suitable processing aides include acrylic polymers such as methyl acrylate copolymers. A specific acrylic process aid is the acrylate sold under the name Acryloid KM® 330, by Rohm and Haas, Inc. Other processing aids are disclosed in The Plastics and Rubber Institute: International Conference on PVC Processing, Apr. 26-28 (1983), Paper No. 17. There are embodiments of the invention containing no such processing aids, but if such processing aids are used they should be added in an amount of up to about 4.0, preferably 0.5 to about 3.0, phr.

[0027] However, another aspect of the invention involves the absence of chlorinated polyethylene (CPE). The use of small amounts of CPE (up to 10 phr) can maintain the heat distoration temperature, but can reduce tensile strength and modulus and thus not meet all of the requirements of ASTM-D 1784, cell class 23448-B. Examples of such CPE additives which should not be used include Tyrin (R) 3611P sold by the Dow Chemical Company. The compositions of this invention should be substantially free of CPE (less than about 1.0 phr). Most preferred, the compositions are free of CPE.

[0028] It has been found for certain embodiments of the invention that lower molecular weight CPVC resins can function as a process aid, i.e., those having an inherent viscosity in the range of about 0.45 to about 0.60, preferably about 0.50 to about 0.56. Specific examples include TempRite 679×705 sold by Noveon, Inc.

[0029] If used, a lower molecular weight CPVC resin should be blended in an amount of up to 50 weight % based on the total amount of CPVC resin, preferably about 10 to about 30%, and more preferably about 10 to about 20%. The most preferred embodiment is 0% low molecular weight CPVC. Such low molecular weight CPVC resins will not adversely affect physical properties and will improve appearance and processability.

[0030] Examples of antioxidants include Irganox 1010 (tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane) sold by Ciba Geigy. These components increase thermal stability and are used in the art primarily for cosmetic reasons, i.e., for delaying color changes. If used, such components may be used in an amount ranging from 0.25 to about 5, preferably about 0.5 to about 1.0, phr.

[0031] Suitable pigments include, among others, titanium dioxide, calcium carbonate, talc, clay, mica and carbon black. Such pigments can be added in amounts ranging from about 0.001 to about 10.0, preferably about 0.01 to about 5.Q, and most preferably up to about 1.0 phr.

[0032] The CPVC formulations can be made in any manner wherein the various components are added together and mixed under heat. For example, the appropriate amount of CPVC resin can be added to a vessel. The remaining ingredients can then be added thereto and mixed. Melt mixing can generally occur at temperatures of from about 150 to about 250° C. (300 to 500° F.). Once the blend is formed, it can be processed in any conventional manner, e.g., using conventional extrusion or molding techniques.

[0033] To obtain a more complete understanding of the present invention, the following examples illustrating certain aspects of the invention are set forth. It should be understood, however, that the invention is not limited in any way to the specific details set forth therein.

EXAMPLES

[0034] Various formulations were prepared to demonstrate certain aspects of the invention. The first formulation, i.e., formulation A, was prepared for comparison purposes, and represents a formulation meeting the requirements of cell class 23447-B and exhibiting suitable processability, but not meeting the requirements of cell class 23448-B. Formulation B meets all of the requirements of cell class 23448-B and demonstrates this invention. Formulations C, D and E are CPVC formulations which are comparative examples which contain CPE and do not meet all of the requirement of ASTM D-1784, cell class 23448-B. The specific components for each formulation are set forth in Table 1, and properties exhibited by the formulations are set forth in Tables 2, 3 and 4. Formulation A was processed and tested at conditions normal for standard CPVC molding compositions (215° C.), while Formulations B, C, D and E were processed and tested at conditions normal for high heat CPVC molding compositions according to the invention (235° C.).

[0035] For formulation A, a CPVC resin was used having an inherent viscosity of 0.68, a chlorine content of 67%, and a fused density of 1.565 grams/cc. Formulations B and C were prepared with a CPVC resin having an inherent viscosity of 0.68, a chlorine content of 70%, and a fused density of 1.607 grams/cc. Formulation D was prepared with a CPVC resin having an inherent viscosity of 0.68, a chlorine content of 70.5%, and a fused density of 1.620 grams/cc. Formulation E included a blend of the same CPVC resin used for formulations B and C, and a lower molecular weight CPVC resin in a 75/25 split of high molecular weight to low molecular weight resin. The lower molecular weight resin had an inherent viscosity of 0.51-0.54, a chlorine content of 70.5% and a fused density of 1.618 grams/cc.

[0036] The CPVC resins for each of Formulations A, B, C, D and E were blended together with the additives and in the amounts indicated below in Table 1. The formulations were then tested for the properties set forth in Tables 2, 3 and 4.

TABLE 1
	FORMULATION
COMPONENT	A	B	C	D	E
CPVC 67% Cl	100
CPVC 70% Cl		100	100		75
CPVC 70.5% Cl				100
Lower Molecular Weight CPVC					25
70.5% Cl (1)
Tin Thioglycolate	3.5	3.5	3.5	3.5	3.5
Acrylic Process Aid	2.0
MBS Impact Modifier	5.0
MBS Impact Modifier (2)		8	8	4	8
Chlorinated Polyethylene			2	8	2
Oxidized Polyethylene	1.25	0.6	0.6	1.0	0.6
Paraffin Wax	1.25	0.9	0.9	1.25	0.9
Antioxidant		0.5	0.5	0.5	0.5
Titanium Dioxide	5.0	3	3	3	3
Carbon Black	0.05				0.12
Yellow Pigment			0.5	0.5
Brown Pigment			0.5	0.5
(1) 0.51-0.54 IV.
(2) higher rubber content and high efficiency MBS.

[0037]

	TABLE 2
	FORMULATION
CELL CLASS PROPERTIES (1)	A	B	C	D	E
Notched Izod (2)	1.6	1.7	1.9	2.1	1.5
(ft-lb/in)
Tensile Strength (3)	8730	7240	7030	7200	6510
(psi)
Tensile Modulus (4)	435,000	363,000	375,000	341,000	369,000
(psi)
Heat Deflection Temp. (5)	101	114	113.5	115	110.5
(° C.)
Acid Weight Gain (6)	1.3	3.0	6.0	0.5	—
(%)
(1) ASTM-D 1784
(2) ASTM-D 256
(3) ASTM-D 638
(4) ASTM-D 638
(5) ASTM-D 648
(6) 93% H2SO4, 14 days, 55° C.

[0038]

TABLE 3
PROCESSABILITY	FORMULATION
PROPERTIES	A	B	C	D	E
Melt Flow Index (1)	8.8	14.5	10.9	20.3	16
(g/10 minutes)
DTS (2)
Torque	18.5	—	—	—	17.2
(Nm)
Time	8.6	3.8	7.8	7.7	4.7
(minutes)
(1) ASTM-D 1238
(2) Brabender Dynamic Thermal Stability/ASTM-D 2538

[0039]

TABLE 4
HOME AND INDUSTRIAL	FORMULATION
USE PROPERTIES	A	B	C	D	E
Quick Burst Strength (1)
(23° C., 1 min: (psi))
2 inch	1630	—	—	—	1550
{fraction (3/4 )} inch	1330	1450	1600	1280	—
Sustained Burst Strength (2)
(180° F., 6 min, 551 psi)	pass	—	pass	fail	Pass
(1) ASTM-D 1599: Schedule 40 fittings
(2) ASTM-D 2846

[0040] From the data shown above, it can be seen that only Formulation B meets all of the requirements of ASTM-D 1784, cell class 23448-B.

[0041] While the invention has been described above in terms of preferred embodiments, it is to be understood that variations and modifications may be used as will be appreciated by those skilled in the art. Such variations and modifications are to be considered within the scope of the invention as defined by the following claims.

Claims

1. An extruded pipe, or a molded or extruded fitting or other piping appurtenance prepared from a CPVC formulation exhibiting suitable processability and meeting the base resin, impact strength, heat deflection temperature, tensile strength, and tensile modulus requirements of ASTM-D 1784, cell class 23448-B, with the proviso that said CPVC formulation is substantially free of chlorinated polyethylene.

2. A pipe, fitting or other piping appurtenance according to claim 1, prepared from a CPVC formulation comprising a CPVC resin having a chlorine content of at least 70% by weight and an inherent viscosity of about 0.65 to about 0.72, and a high rubber content and high efficiency MBS impact modifier, said CPVC formulation having a melt flow index of about 1 to about 20g/10 minutes and a DTS time of at least 3 minutes at 235° C./35 r/m.

3. A pipe, fitting or other piping appurtenance according to claim 2, prepared from a CPVC formulation having a melt flow index of about 5 to about 20 g/10 minutes, and a DTS time of at least 5 minutes.

4. A pipe, fitting or other piping appurtenance according to claim 1, meeting the acid weight gain requirements of ASTM-D 1784, cell class 23448-B.

5. A pipe, fitting or other piping appurtenance according to claim 3, wherein said formulation further comprises a lower molecular weight CPVC resin having an inherent viscosity of about 0.45 to about 0.60, in an amount of about 10 to about 20 weight %.

6. A pipe, fitting or other piping appurtenance according to claim 2, wherein said formulation comprises a CPVC resin with a chlorine content of about 70 to about 73% by weight and an inherent viscosity of about 0.65 to about 0.72, about 2 to about 4 phr of tin stabilizer(s), about 5 to about 10 phr of MBS impact modifier(s), up to about 3 phr of acrylic process aid(s), about 0.4 to about 5 phr lubricant(s), and about 0.25 to about 1.0 phr antioxidant(s).

7. A CPVC formulation comprising: a CPVC resin having a chlorine content of at least 70% by weight and characterized by an inherent viscosity of about 0.60 to about 1.0, from about 3 to about 15 phr of a high rubber content MBS and/or ABS impact modifier, said formulation meeting the base resin, impact strength, heat deflection temperature, tensile strength, and tensile modulus requirements of ASTM-D 1784, cell class 23448-B, with the proviso that said CPVC formulation is substantially free of chlorinated polyethylene.

8. A CPVC formulation according to claim 7, meeting the acid weight gain requirements of ASTM-D 1784, cell class 23448-B.

9. A CPVC formulation according to claim 7, comprising a CPVC resin having a chlorine content of at least 70% by weight and an inherent viscosity of about 0.65 to about 0.72, and a high rubber content and high efficiency MBS impact modifier, said CPVC formulation having a melt flow index of about 1 to about 25g/10 minutes and a DTS time of at least about 3 minutes at 235° C./35 r/m.

10. A CPVC formulation according to claim 7, comprising a CPVC resin having a chlorine content of at least 70% by weight and an inherent viscosity of about 0.65 to about 0.72, and a high rubber content and high efficiency MBS impact modifier, said CPVC formulation having a melt flow index of about 5 to about 20 g/10 minutes and a DTS time of at least about 5 minutes.

11. A CPVC formulation according to claim 9, further comprising a lower molecular weight CPVC resin having an inherent viscosity of about 0.45 to about 0.60, in an amount of about 10 to about 20 weight % of total CPVC resin.

12. A CPVC formulation according to claim 9, comprising a CPVC resin with a chlorine content of about 70 to 73% by weight, about 2 to about 4 phr of a tin stabilizer(s), about 5 to about 10 phr of MBS impact modifier(s), up to about 3 phr of acrylic process aid(s), about 0.4 to about 5 phr lubricant(s), and about 0.25 to about 1.0 phr antioxidant(s), and containing no polyorganosiloxane-containing impact modifier.

13. A CPVC formulation according to claim 7, further comprising a lower molecular weight CPVC resin having an inherent viscosity of about 0.45 to about 0.60, in an amount of about 10 to about 20 weight % of the total CPVC resin.

14. A CPVC formulation according to claim 9, in the form of a fitting or piping appurtenance.