JPH01144409A - Hydrophylic sequence copolymer of vinylidene fluoride and n-alkylacrylamide and its production - Google Patents

Abstract

PURPOSE: To prepare the copolymer having high water-permeability, useful as filer membranes, etc., by polymerizing vinylidene fluoride in an aqueous emulsion using a free radical initiator, and further polymerizing the resulting latex by adding N-substituted acrylamide, etc.,. and methacrylate.

CONSTITUTION: The objective copolymer is obtained by polymerizing vinylidene fluoride in an aqueous emulsion in the presence of a free radical initiator to obtain a vinylidene fluoride polymer latex, adding 1-30 wt.%, based on total weight of the added free radical initiator and the copolymer, of an amide having unsaturated terminal group such as N-lower alkyl acrylamide, N,N-di-lower alkyl acrylamide and 1-vinyl-2-pyrrolidinone and 0-29 wt.%, based on total weight of the added free radical initiator and the copolymer, of a lower alkyl methacrylate to 70-99 wt.% of the latex thus obtained, and polymerizing in the presence of the vinylidene fluoride polymer latex.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to hydrophilic copolymers of vinylidene fluoride, more particularly vinylidene fluoride and N-alkylacrylamide or 1-vinyl- The present invention relates to the production of hydrophilic sequential copolymers of 2-pyrrolidinone and optionally alkyl methacrylates. The polymers are useful in forming filtration membranes, coatings, films and fibers.

BACKGROUND OF THE INVENTION Fluorocarbon polymers, such as polyvinylidene fluoride, are resistant to chemical and biological attack. However, they are hydrophobic, which limits their usefulness in forming filtration membranes. When filtering aqueous solutions, hydrophilic membranes are desirable in order to allow the liquid to pass through quickly. Hydrophobic polymers are also incompatible with polymer additives and other polymers.

US Pat. No. 4,340,482 discloses the modification of such polymers to provide hydrophilic membranes. In this method, the surface of a preformed polymer is treated with a base to provide an active moiety to which a hydrophilic reagent such as an amino acid can be grafted. For example, a mixture of glycine, sodium hydroxide, and water is used to graft glycine in the form of glycinate onto the surface of a preformed polyvinylidene fluoride microporous membrane.

The present invention provides polyvinylidene fluoride in which the polymer is rendered not only superficially (itself) hydrophilic; the polymer retains its excellent physical and chemical resistance.

SUMMARY OF THE INVENTION In accordance with the present invention, about 70,799 weight percent of a preformed vinylidene fluoride polymer is combined with N-lower alkyl acrylamide, N,N-di-lower alkyl acrylamide, and 1-
from about 1 to 30% by weight of at least one terminally unsaturated amide selected from the group consisting of vinyl-2-pyrrolidinone;
and from 0 to about 29 weight percent lower alkyl methacrylate.

Also provided is a method for producing a hydrophilic sequential copolymer of vinylidene fluoride and an amide containing terminal unsaturation, comprising: A) polymerizing vinylidene fluoride in an aqueous emulsion in the presence of a free radical initiator to form a vinylidene fluoride polymer latex. B) The latex is then combined with: - an additional free radical initiator and about 1-30% based on the total weight of the fist copolymer: - N-lower alkyl acrylamide, N,N-di-lower alkyl acrylamide, and addition of a monomer containing at least one terminal unsaturation-containing amide selected from the group consisting of l-vinyl-2-pyrrolidinone; and from 0 to about 29% by weight lower alkyl methacrylate, based on the total weight of the copolymer; and C) polymerizing the emulsified monomer in the presence of the latex to form a copolymer latex of the vinylidene fluoride and the monomer.

DETAILED DESCRIPTION OF THE INVENTION The copolymers of the present invention are based on vinylidene fluoride polymers, which are structurally stable and chemically inert, thus forming thin microporous filtration membranes.

It is useful for encouraging people. However, vinylidene fluoride homopolymer has low water permeability. Hydrophilic copolymers are provided by reacting such polymers with certain hydrophilic terminal unsaturation-containing amides. Ultrafiltration membranes formed from such copolymers have very high water permeability. This copolymer is also more compatible with both other polymers and polymer additives with high surface energies such as inorganic oxides. When the mixture of the amide and lower alkyl methacrylate is reacted with a vinylidene fluoride polymer, it is less hydrophilic than the copolymer of the amide, but surprisingly has better water permeability and better solute retention. A terpolymer having the following is provided.

The copolymers of the present invention are polymerized amides (or amides and methacrylates) in which a preformed vinylidene fluoride polymer latex is combined in the presence of a free radical initiator so that the resulting hydrophilic copolymer is chemically bonded to the vinylidene fluoride polymer.
It is a sequential polymer reacted with a hydrophilic amide monomer containing terminal unsaturation so as to have the following properties.

As used herein for brevity, the meaning of the term "vinylidene fluoride polymer" includes normally solid, high molecular weight homopolymers and copolymers with other fluorocarbon monomers. Such copolymers include tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene,
Included are those containing at least 50 mole % vinylidene fluoride copolymerized with at least one comonomer selected from the group consisting of vinyl fluoride and pentafluoropropene (e.g., GB 827.308). copolymers comprising at least about 70 to 99 mole percent vinylidene fluoride and correspondingly 1 to 30 percent tetrafluoroethylene;
% vinylidene fluoride and 1 to 30% hexafluoropropene (e.g., U.S. Pat.
78.399); and about 70-99
A copolymer consisting of mol % vinylidene fluoride and 1 to 30 mol % trifluoroethylene). Further, a terpolymer of vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene and a terpolymer of vinylidene fluoride, trifluoroethylene, and tetrafluoroethylene described in U.S. Pat. No. 2,968,649 are also available. Polymers also
It represents a class of vinylidene fluoride copolymers that can be used as preformed polymers in the production of sequential copolymers practiced in this invention.

Suitable methods for producing such vinylidene fluoride polymers are described, for example, in U.S. Pat.
No. 569.978, known in the art. In these processes, a reactor equipped with a stirrer and heat control means is charged with about 0.000 mA, based on the total amount of monomer used in the process. O1 to 0.5% by weight of fluorinated surfactant, approximately 0.0% based on monomer
Charge 3-0.30% by weight long chain saturated wax or oil (to prevent polymer from sticking to reactor surfaces) and deionized water. This charge is heated (1
Deoxygenate by heating (10° C.) and stirring (50-72 rpI11), degassing without stirring and bring to the desired reaction temperature (60-95° C., preferably 75° C.). Based on the total amount of monomer used in the process, about 0.
The reactor was heated to about 14.6 to 69,0 atm by adding 1 to 8 wt. (approximately 200~1000psi
g), preferably 44.2 to 58.8 atm (6
50-850 psig). Polymerization is initiated by the addition of a free radical initiator such as diisopropyl peroxydicarbonate emulsified in water using a surfactant. The monomers, initiator and optional additional chain transfer agent are then added stepwise to the reactor over the duration of the polymerization cycle until the desired amount of monomer has polymerized to form the vinylidene fluoride polymer latex. Or add continuously.

Hydrophilic amide monomers containing terminal unsaturation suitable for use in the present invention include N-vinylpyrrolidinone and lower alkyl (C, ~
N-alkylacrylamides substituted with C4) groups are included. Examples of such acrylamides include N-methylacrylamide, N-ethylacrylamide, N-
Propylacrylamide, N-butylacrylamide,
These include N,N-dimethylacrylamide and N,N-diethylacrylamide. Acrylamide itself is expected to increase hydrophilicity, but it does not react efficiently with vinylidene fluoride polymers.

The sequential copolymers of the present invention may also contain lower alkyl methacrylates (01-C1), such as methyl methacrylate. The methacrylate provides membranes with improved solute retention and water permeability even though the methacrylate-containing polymer has low hydrophilicity.

To provide significant hydrophilicity, at least about 1%
of amide is required. By the method of the invention, approximately 30
Sequential copolymers containing up to % by weight of amide can be prepared. When copolymers are used to form filtration membranes, lower amounts of amide should be used since amounts greater than about 20% will render membranes made from such polymers impermeable. . Accordingly, compositions suitable for filtration membranes contain about 1-20% by weight of amide;
The remainder is vinylidene fluoride polymer and optionally about 29
The amount of alkyl methacrylate should be up to % by weight. Preferred alkyl methacrylate-containing polymers for the membrane contain about 70-90% by weight vinylidene fluoride polymer units, about 5-15% by weight amide polymer units, and about 5-1% by weight vinylidene fluoride polymer units.
Contains 5% by weight alkyl methacrylate polymer units.

All percentages given are based on the total weight of the sequenced polymer.

The amide (or amide and methacrylate) is added after the vinylidene fluoride polymer latex is formed. The amide containing terminal unsaturation and the acrylate, if used, are added to the fluoride in the reactor at the end of the polymerization, preferably immediately after the vinylidene fluoride feed to the reactor is completed and before the pressure in the reactor is reduced. Although it is desirable to add it to the vinylidene chloride copolymer latex, this is not essential.

This is not only more convenient (but also maximizes the amount of reaction between the vinylidene fluoride polymer and the added monomers).

In addition, when adding amide alone, in order to minimize the amount of amide homopolymer, it is necessary to maximize "copolymerization efficiency".
It is advantageous to quickly add the entire amide charge to the reactor to obtain (eg, the percentage of comonomer units chemically bonded to the vinylidene fluoride polymer). The optimum addition rate of amide monomer will vary depending on the scale of the polymerization process, and this rate can be determined experimentally in each case. For example, in the example below using a 7.5742 (2 gallon) reactor, a monomer feed rate of 101 g/min results in a copolymerization efficiency of 98%, whereas 48 and 36 g
At a speed of 1/min, the copolymerization efficiency was only 83% and 87%, respectively. However, the comonomer charge is alkyl methacrylate.

Rapid addition does not increase copolymerization efficiency if the copolymer also contains copolymerization. Other factors that influence copolymerization efficiency are the type and amount of chain transfer agent and the ratio of reaction components.

The amide monomer can be added as an aqueous solution and the alkyl methacrylate can be added as an aqueous emulsion. If both amide and methacrylate are used, they are added as an aqueous emulsion. Free radical initiators are added both during monomer feed and during polymerization. The same pressures, temperatures and initiators can be used during the polymerization of vinylidene fluoride.

The total reaction time for both polymerizations generally ranges from 1 to 8 hours, preferably from 2 to 5 hours. The solids content of the latex generally ranges from about 10 to 25% by weight.

[Examples] Hereinafter, the present invention will be further illustrated by Examples, but these Examples do not limit the present invention at all. In the following examples, unless otherwise specified, parts are parts by weight.

VFz DMA 85 15 1:l Bommer 7 with electric stainless steel 4-blade stirrer,
57J2 (2 gallon) horizontal reactor with 44 mL of deionized water
An initial charge consisting of 12.1% by weight ammonium perfluorooctanoate surfactant aqueous solution at 100 mC and 4 g of paraffin wax was introduced. This initial charge was heated to 110° C. using a mixture of steam and water in the reactor jacket with stirring (72 rpm) and then deoxygenated by venting without stirring. Next, a stirrer? Restarted at 2 rpm and cooled the reactor to 75°C.

A 5% by weight aqueous solution of 2-propanol (
107g) from a stainless steel cylinder at 2.36 at
The injection was performed at a nitrogen pressure of 20 psig.

In this reactor, 55.4 atm (800 psig)
Vinylidene fluoride (VF, ) at a reactor pressure of 45.2 atm (650 p
si) (VF, approximately 450 g).

A cooled reactor containing 2% by weight of diisopropyl peroxydicarbonate (IPP) and 0.15% by weight of a fluorinated surfactant (ammonium perfluorooctanoate) was added to the reactor using a non-ventilated stirrer. The initiator aqueous emulsion was injected at a rate of approximately 8 mI2/min. Polymerization started after an 18 minute induction period as indicated by the pressure drop. During the polymerization, the reactor was supplied with V F a in advance to feed the initiator emulsion at the rate necessary to sustain the reaction (approximately 2 mβ/min) and to maintain the pressure at 45.2 atm (650 psLg). Continuous feeding was carried out until a total of 1022 g was fed, including the amount charged. This took 1 hour and 11 minutes. Then, the supply of VF was stopped.

Next, 450 g of a 40% by weight N,N-dimethylacrylamide (DMA) aqueous solution was added to the reactor from a stainless steel cylinder at 52.0 atm (750 psLg).
) at a rate of 36 gDMA/min over 5 minutes. The reactor was charged with an IPP initiator emulsion (2
% by weight) was injected at a rate of 2 mβ/min. 35 mJ2 of deionized water was injected into the DMA supply line to drive residual DMA into the reactor. The pressure is 54.8 atm (79
0 psLg). The final VF/DMA ratio was 85,715 by weight and 90/10 by molar ratio. The total amount of VFO and DMA supplied was 1202 g. The total amount of IPP emulsion used is 387 mβ (IPP 7.7 g)
was.

After the end of the DMA feed, stirring of the reactor was continued for 2 hours at 75°C. The pressure is 52.7 atm (760 psi)
g). Stirring was then stopped and residual gas was vented from the wet water-cooled trap and carbon column.

Pass the latex product through cheesecloth? Filtered and weighed. Weight 4982g, solids content 14.2%
, pH was 3.9. The weight of the dry coagulum was 41 g and the deposit was 2 g. The total polymer yield was 749g (
The yield was 62.3%). The average polymerization rate is 36g/β/
It was time.

This latex did not clump by freezing and was then dried overnight in a Teflon polymer lined dish in an oven at 90°C. A portion of the obtained copolymer was compression molded at 180°C to obtain a transparent flexible film. A portion of this film was weighed and extracted with boiling deionized water to remove the polyDMA. The aqueous extract was evaporated and the residue (polyDMA) was dried and weighed. The extractable content (%) was calculated. The DMA copolymerization efficiency (%) was then calculated as follows: Water absorption of the film was measured by weighing before and after immersion in water for 24 hours.

An ultrafiltration membrane was manufactured by a method similar to that of US Pat. No. 4,384,047. Stir electromagnetically 108
20% by weight of the above copolymer by heating to
A solution of 5% by weight of glycerin and 75% by weight of triethyl phosphate was prepared. After allowing the clear and viscous solution to stand for air bubbles to disappear, 1. Clear 30.5 cm using a Gardner knife set to 40 mil.
Cast on 12 inch x 12 inch glass plates at 108°C. The casts were left in a hooded compartment for 5 minutes and then immersed in a tap water bath at 15° C. for 4 days. The cohesive top layer was separated from the residual film and cut into circular pieces with a diameter of 90 mm using a punching die. This membrane was manufactured by Amicon (Am1con).
The test was carried out using an ultrafiltration system with a narrow channel, Model TCP-10, manufactured by Co., Ltd. The test results are shown in Table 1.

■U VF* DMA 90 10 1 copolymer synthesis method is similar to the method described in Example 1, with the following exceptions: l) Monomer ratio VF, /DMA is 90/10 by weight;
The molar ratio was 9377; 2) no chain transfer agent was used; 3) a 32 minute reaction slowdown period was allowed after completion of step 1 and before step 2.

Regarding the type and ratio of ingredients, please refer to VF, 913g, 19
．． 522 g of 5% by weight DMA aqueous emulsion and 293 mβ of 2% by weight IPP emulsion were used. pressure is 4
It ranged from 6.6 to 7.8 atm (670 to 100 psi). 7. Vent the reactor after step 1 (VF, polymerization) and during step 2 (DMA addition and reaction).
It was sealed with nitrogen at 8 atm (100 psL). Total reaction time was 2 hours and 45 minutes. The weight of the filtered latex is 5870 g, and its solid content is 1
It was 2.8%.

Total polymer yield including 9 g of coagulum and 3 g of deposits was 76
2g (yield 75%). The average polymerization rate is 53g/
It was j2/hour. The test results are shown in Table 1.

Takumiyu VF* DMA 88 12 l:l The polymer synthesis method is similar to that described in Example 1, with the following exceptions: 1) The monomer ratio VF2/DMA is 88/12 by weight;
The molar ratio was set to 9278; 2) Isotron (l5OTRO) was used as a chain transfer agent.
N) (registered trademark name)-11J was used.

1062g of VFa, 286g of 50% DMA aqueous solution and 2
A weight percent IPP emulsion of 492 m°C was used. The pressure is 53.7~31.6atm (775~450ps
It was within the range of i). Total reaction time was 2 hours and 20 minutes.

The weight of the filtered latex was 5621 g and its solids content was 18.9%. The total polymer yield is 1
It was 136g (yield 94%). The average polymerization rate is 96
g/It/hour. The test results are shown in Table 1.

Takumi A VF, DMA 80 20 1:I Bo 1 mer synthesis method uses a monomer ratio of VF, /DMA of 80/1 by weight.
The method is similar to that described in Example 1, except that the molar ratio is 86/14. Regarding the types and ratios of the components, 5% by weight 2-propertool aqueous solution 115g% VF, 9
57g, 40wt% DMA aqueous solution 597g and 2wt%
IPP emulsion 365mj2 was used. pressure is 4
5.2~53.7atm (650~775psig
) range. Total reaction time was 3 hours and 50 minutes. The weight of the filtered latex was 530 g and its solids content was 13.9%. 33g of coagulum and 3g of deposits
The total polymer yield including
)was. The average polymerization rate was 36 g/β/hour. The test results are shown in Table 1.

example".

VF, DMA MMA 85
5 10 E1 The terpolymer synthesis method uses three types of monomers at a ratio of VF, /DMA/M.
MA weight ratio: 8515/10, molar ratio: 90/7/3
Same as Example 1 except that VF was used as VF
z 1026g; risotron-11” (CF(J,
186g; DMA60g, base washed MMA120g
and “Surflon 5IIISJ fluorine-based surfactant 0.
400 g of an aqueous emulsion containing 4 g; and 2% by weight IPP Emulsigon 676 mj2 were used. Pressure is 61.9~42.5atm (895~610ps
i) range. Total reaction time was 2 hours and 13 minutes. The weight of the clean latex was 5531 g, its solids content was 15.5%, and its pH was 3.0. Total polymer yield was 911 g (76% yield), average polymerization rate was 76 g/42/hr. The test results are shown in Table 2.

The medical synthesis method was the same as in Example 5, except that the monomer ratio VF*/DMA/MMA was 80/10/10 by weight and 86/7/7 by molar ratio.

VF, 958g, r itcl-114 (CFCl
)86g; DMA120g, base washed MMA 120
g and “Surflon 5IISJ fluorine-based surfactant 0.
an aqueous emulsion containing 4g; and 2% by weight IP
P emulsion 385mn was used.

The pressure is 57.5 to 44.9 atm (830 to 645
psi) range. Total reaction time was 2 hours and 25 minutes. The weight of the filtered latex is 5449g,
Its solids content was 15.2% and pH was 3. Total polymer yield was 901 g (75% yield). The average polymerization rate was 71 g/12/hour. Table 2 shows the test results.
Shown below.

VF, DMA MMA 70 10 20 丑ヱ-, I? lJ: The synthesis method uses three types of monomers at a ratio of VF, /DMA/M
MA weight ratio: 70/10/20, molar ratio: 79/7/
The method was similar to that of Example 1, except that 14 was used. First, 699 g of V F z was polymerized, and after stopping the reaction for 30 minutes, an aqueous amide-acrylic emulsion (33.3% by weight of MMA, 16.7% by weight of DMA and "Surflon 5 ILIS J fluorine surfactant") was added. (containing 0.15% by weight) was added.I
The total amount of PP initiator emulsion 3 used was 459 mJ2 (
IPP9.2g). Pressure is 46.2-24.1
atm (665-340psi). Total reaction time was 4 hours and 21 minutes. The weight of the clean latex is 5998g, and its solids content is 12.5
In weight percent, the pH was 4.0. Total polymer yield including 26 g of coagulum and 3 g of deposits was 776 g (yield 77.
6%). Average polymerization rate is 35 g/i! , it was 7 hours. The test results are shown in Table 2.

The Takudan synthesis method uses a monomer composition (VF, /VP, weight ratio of 8
5/15, molar ratio 91/9).

VFt1026g, 5% by weight 2-propertool aqueous solution 1
07 g, 445 g of 40 wt% VP aqueous solution and 2 wt% I
PP emulsion 514mI2 was used. The pressure is 57
．． It ranged from 8 to 43.9 atm (835 to 630 psi). Total reaction time was 3 hours and 53 minutes. The weight of the filtered latex was 3727 g, its solids content was 8.3%, and its pH was 3.2. Total polymer yield was 660 g (55% yield). The average polymerization rate is 3
It was 1g/(1/hour).The test results are shown below.

Copolymer melting temperature 166.170 (double peak) Heat of fusion (J/g) 54 Water absorption (
%) 0.15 Hot water extract (%) 0.19 vp Copolymerization efficiency (%) 98.7 Melt flow rate (g/
10 minutes, 180℃, zt, sxg) Water permeation amount of membrane (2
, 36 atm (20 psi) ) Initial value (mg/c 7 minutes) 0.28 Final value (m 12 /
c i/min) 0.17 0.1% blue dextran solution (2,36atn+ (20psi)) permeation amount (m
(1/crd 7 minutes) 0.15 Retention rate (%) 80 [Effects of the invention] The polymer of the present invention is a polyvinylidene fluoride homopolymer (rKYNAR (registered trademark name)) of the control example whose characteristics are shown in Table 2. ) 461J resin) 0 The polymers of the present invention provide higher water permeation while still retaining macromolecules.
Provides improved water permeability to the filtration membrane. Hydrophilic amides are chemically bonded throughout the polymer, increasing the wettability not only of the surface but of the entire polymer. This not only improves its filtration properties, but also its compatibility with other polymers and polymer additives with which it is mixed.

Claims (15)

[Claims] (1) Preformed vinylidene fluoride polymer about 70~
99% by weight of N-lower alkyl acrylamide, N,
N-di-lower alkyl acrylamide and 1-vinyl-2
- at least one selected from the group consisting of pyrrolidinones;
A hydrophilic sequential copolymer reacted with about 1 to 30% by weight of a terminally unsaturated amide and 0 to about 29% by weight of a lower alkyl methacrylate. (2) about 1 to 20% by weight of amide polymer units and about 8
Copolymer according to claim 1, characterized in that it contains from 0 to 99% by weight of vinylidene fluoride polymer units. (3) about 70-90% by weight vinylidene fluoride polymer units, about 5-15% by weight amide polymer units, and about 5-90% by weight vinylidene fluoride polymer units;
Copolymer according to claim 1, characterized in that it contains 15% by weight of lower alkyl methacrylate polymer units. (4) A copolymer according to claim 2 in the form of a filtration membrane. (5) A copolymer according to claim 3 in the form of a filtration membrane. (6) The copolymer of claim 1 containing about 80-90% by weight of vinylidene fluoride homopolymer units and about 10-20% by weight of N,N-dimethylacrylamide polymer units. . (7) The copolymer according to claim 3, wherein the vinylidene fluoride polymer is a homopolymer of vinylidene fluoride. (8) A method for producing a hydrophilic sequential copolymer of vinylidene fluoride and an amide containing terminal unsaturation, comprising: A) polymerizing vinylidene fluoride in an aqueous emulsion in the presence of a free radical initiator to obtain a vinylidene fluoride polymer; forming a latex; B) then adding to the latex: an additional free radical initiator; and about 1 to 30% by weight, based on the total weight of the copolymer;
C) adding a monomer containing at least one terminal unsaturation-containing amide selected from the group consisting of N-lower alkyl acrylamide, N,N-di-lower alkyl acrylamide, and N-vinylpyrrolidinone; and C) adding the monomer to the latex. The process comprises polymerizing vinylidene fluoride and the monomer to form a copolymer latex in the presence of a monomer. (9) the monomer contains up to about 29% by weight of lower alkyl methacrylate, based on the total weight of the copolymer, such that the vinylidene fluoride has both the amide and the lower alkyl methacrylate copolymerized therewith; 9. The method according to claim 8, characterized in that: (10) Addition of about 1 to 20% by weight of amide based on the weight of the polymer
The method described in section. (11) about 5 to 15% by weight of the above amide and about 5 to 15% by weight of the above amide;
9. A method according to claim 8, characterized in that % by weight of said lower alkyl methacrylate is added. (12) The method according to claim 8, characterized in that a chain transfer agent and a fluorosurfactant are present. (13) Temperature of about 60-95°C and 14.6-69.0°C
9. The method of claim 8, wherein the method is carried out at a pressure of about 200 to 1000 psig. (14) A method for producing a hydrophilic sequential copolymer of vinylidene fluoride and an amide containing terminal unsaturation, comprising: A) a preformed vinylidene fluoride homopolymer latex containing - based on the total weight of the copolymer: 20% of N-
rapidly adding at least one terminal unsaturation-containing amide selected from the group consisting of lower alkyl acrylamide, N,N-di-lower alkyl acrylamide and N-vinylpyrrolidinone, and a free radical initiator; and B) said latex. The above-mentioned manufacturing method is characterized in that the above-mentioned amide is polymerized to form a copolymer of the above-mentioned vinylidene fluoride and the above-mentioned amide in the presence of . (15) The method according to claim 13, wherein the amide is N,N-dimethylacrylamide.