Xiong Zongling
Foshan Polyva Materials Co.,Ltd.,China
Abstract The influence of PVA water soluble film on the quality of llaundry capsule was discussed from three aspects:appearance,manufacture and use.The basic properties of several mainstream PVA membranes on the market related to laundry capsules were evaluated.The results show that the mist value of the film affects the appearance of the capsules.The higher the mist value is,the worse the transparency of the capsules is.The mechanical properties of the film affect the shape of the capsules,the tensile strength ＞ 35 Mpa,elongation ＞400%,modulus ＞ 50 Mpa,the shape of the capsules is more three-dimensional;The water solubility of the film can affect the production of the capsules,and the production of the capsules is smooth when the film breaking speed is greater than 20 ～30 s and the dissolution speed is 40～60 s.The film compatibility index reflects the effect of the capsules washing machine.The shorter the dissolution time of the compatibility,the less the residue of the capsules after washing.
Key words pva water-soluble film;laundry capsules;property
In 2000,P＆G’s first laundry gel capsule was born in the UK;Twelve years later,P＆G launched three chamber laundry capsules in North America and detonated the market,selling 1.7 billion in that year;In 2014,laundry capsules were introduced into China.After that,NICE,Liby,Whealth Lohmann Centralin,Unilever and other enterprises successively followed up and launched functional laundry capsules[1].Laundry gel capsule products are in line with the concentration development trend of the washing industry,can effectively reduce environmental pollution and promote the product structure adjustment and industrial upgrading of China’s washing industry[2].However,due to the rapid development of the market,the lack of experience of many enterprises and the imperfection of relevant supporting technologies,the use of products is not ideal.In addition,the relevant norms of the industry can not keep up,resulting in a mixture of products in the market and affecting the benign development of products in the industry.
The quality of laundry gel is related to the water-soluble film of the packaging and the washing liquid of the contents.The washing liquid affects the washing function and PVA water-soluble film affects the appearance,manufacturing performance and use experience of washing capsules.The draft for comments on the industry standard of laundry capsules pointed out that the quality indicators of laundry capsules include bitterness,tightness,stability,pH value,total phosphorus pentoxide,solubility,pressure strength,specified decontamination power of dirty cloth,etc.The indexes related to the liquid matrix include stability,pH value,total phosphorus pentoxide and the decontamination power of the specified cloth;The indexes related to the film include bitterness,sealing,solubility and compressive strength.
2.1 Impact on appearance
The appearance index of laundry capsules is mainly transparency.The high transparent capsules can show the gorgeous colors of the content,and the colorful colors can attract people’s eyes and give people a higher feeling.European and American consumers prefer to use matte outer packaging film,which gives people a quiet and generous feeling and thinks it is safer.The haze of PVA film is directly related to the transparency of laundry capsules.The haze of PVA film is directly related to the transparency of capsules.The higher the haze value of the film,the worse the transparency of the packaged capsules
2.2 impact on manufacturing performance
During the molding process,the packaging machine needs to be packed by vacuum and water bonding and pressurization.This process has high requirements for PVA membrane.Some indexes of PVA water-soluble membrane are related to the stability of capsules and product modeling.First of all,the friction coefficient of PVA affects the smooth unwinding and edge setting of production.When the friction coefficient is high,the film unwinding is not smooth,it is easy to wrinkle,the edge setting is unstable,and the capsules are easy to wrinkle,resulting in liquid leakage.Second,the mechanical properties of the film affect the vacuum pumping and capsule molding.Mechanical properties include tensile strength,ductility and elastic modulus.High tensile strength,high elastic modulus and good elasticity of the capsules;With high ductility,the film is easy to be formed in a deep cavity and has a good sense of three-dimensional modeling.Third,the sealing performance of the film.The sealing strength of the film is high,the edge sealing is firm,the pressure resistance of the capsule is good,and it is not easy to squeeze and burst during transportation.The wet viscosity is good,the film is easy to be sealed on the machine,the sealing stability is high in high-speed production,and the phenomenon of "false welding"is not easy to occur.Fourth,the micropore rate of the film.If the micropore rate is high,the capsules will leak.Fifth,the water solubility of the film.Water sealing technology is used for film sealing.If the film dissolves too fast,it is easy to break the film during sealing.If it is too slow,it will not produce enough viscosity,resulting in unstable sealing.
2.3 Impact on service performance
The effect of PVA water-soluble membrane on the performance of laundry capsules is mainly reflected in the dissolution rate.The use mechanism of laundry capsules is to contact the PVA film with water to dissolve it and release the content laundry liquid.Theoretically,the faster the dissolution is,the better.However,due to safety inspection,the industry stipulates that the gel capsule should be broken in more than 30 s and the residue of PVA water-soluble film after washing greatly affects the use feeling of consumers.According to the feedback in sale market,consumers require that the use of laundry capsules for washing can achieve no residue in the fast washing mode.Therefore,laundry capsules need to have good solubility at low temperature and less water.Meanwhile,during transportation and storage,the laundry capsules will also be affected by high temperature,which will reduce the solubility of the film.Therefore,it is necessary to investigate the PVA film dissolution time of PVA water-soluble membrane,the film breaking time after wrapping the laundry capsules dissolution time and stability of solubility after storage under extreme conditions (test conditions set at 50 ℃,storage conditions above 80% RH).
The evaluation indexes of PVA water-soluble film affecting the quality of laundry capsule products include haze,friction coefficient,tensile strength,ductility,elastic modulus,sealing strength,pinhol,single film dissolution (24 ℃) and compatibility.For these indicators,different film manufacturers have their own characteristics.The author selects some representative film products for testing.Some test items will not be tested temporarily due to the use of equipment in the author"s unit.Test samples:domestic films GC1 #,GC2#,GC3 #,GC4 #,imported films Jk1 #,JK2 #.
3.1 Haze and transmittance
The haze tester is used and tested with reference to ASTM D1003-61 (1997).The test results are shown in Figure 1 and Figure 2.It can be seen from Figure 1 that among the tested films,GC1 #,JK2 #,has the highest haze.As can be seen from Figure 2,the order of display effect from good to bad is:JK2 # → GC3 # →GC2 # → Jk1 # → GC4 # → GC1 #.According to the corresponding test data,the lower the haze,the higher the transmittance,and the better the display of capsules.
Figure 1.Haze of PVA film from different manufacturers
Figure 2.The appearance of PVA Laundry Gel from different manufacturers
Figure 3.Tensile strength of PVA film from different manufacturers
Figure 4.PVA film elongation rate of different manufacturers
Figure 5.Elastic modulus of PVA film from different manufacturers
3.2 Mechanical property test
The universal tensile testing machine is used.Refer to GB13022-91 test method for tensile properties of plastic films.The test results are shown in Figure 3,Figure 4 and Figure 5.The tensile strength determines whether the film is easy to be broken in the vacuum absorption link.Therefore,the higher the tensile strength,the more suitable the film is for the machine.According to experience,the film above 35 MPa has better effect in production.In the test samples,except GC1#,all reached above 35 MPa,and GC3# was the best.The elastic modulus affects the touch of the capsule after forming.The higher the elastic modulus,the better touch of the capsule is after forming.The elastic modulus range of PVA suitable for capsule forming is 50～150 MPa.Jk2#feels the best and GC1# feels the worst.The elongation rate determines whether it is easy to form.Generally,the elongation rate of PVA packaging film is required to be greater than 350%.For molds that need three-dimensional modeling and the elongation ratio is greater than 1∶2,the film elongation rate should be greater than 400%.The films in this evaluation meet this requirement.As can be seen from Figure 2,GC2 #,GC3 #,GC4 # and Jk1# have good three-dimensional effect,GC1 # has slight retraction,JK2 # has slight stretching and collapse.
3.3 Single film solubility test
Single film dissolution (24 ℃):Use the die which with Outer diameter 6 × 6 cm,inner diameter 4.5 ×4.5 cm to cut samples,take 3 samples of each kind.After measuring the thickness,take 1,000 mLpure water at 24 ℃ with a beaker,and turn on magnetic stirring to make the vortex depth 200 mL.Insert the sample into the water and start the timer to record the disintegration time and complete dissolution time of the film.The test results are shown in Figure 6.The water solubility of the film reflects the dissolution rate of the film.The film dissolves fast and the capsules dissolve fast in the process of use.In the production process,because the capsule sealing adopts the water sealing technology,that is,by applying water on the film surface,the film surface is dissolved to produce the adhesive force,which makes the two layers of films fit together.If the dissolution speed is too fast,the film will break and cannot be produced.If the dissolution is slow,it will not produce enough viscosity,resulting in weak edge sealing.According to experience,the more suitable film breaking speed is greater than 20 ～ 30 s and the dissolution speed is 40 ～60 s.In this test,except GC1# water solubility is slow,the other models are in the appropriate range.
Figure 6.Water solubility of PVA film from different manufacturers
3.4 Compatibility test
Laundry capsules packaging testing machine is used and molded with 20 g mold.The standard liquid produced in the same batch is selected for the content matrix,and each film is wrapped with 3 condensed capsules.Store the wrapped capsules under high temperature and humidity (50 ℃,80% RH) for 48 h,take them out and cool them for testing.Measure 1,000 mL pure water at 24 ℃ with a beaker,turn on magnetic stirring to make the vortex depth 300 mL,put the capsule sample into water,start the timer at the same time,and record the film breaking time and film complete dissolution time of the capsule.The test results are shown in Figure 7 and Figure 8.Compatibility evaluation refers to the matching of the film with the washing liquid and the stability of the beads during storage.The same washing liquid uses different PVA water-soluble films and is aged for 48h under extreme conditions (50 ℃,80% RH),which is equivalent to simulating natural aging for about 1 year.Test the dissolution time of solidified capsules after aging to simulate the conditions used by consumers.The faster the dissolution rate,the less the film residue after washing.By comparison,the gel capsules whose dissolution time is less than 450 s in the general compatibility test results can still achieve no film residue after washing when using the 15 min fast washing mold.If the compatibility dissolution time is more than 10 min,there is a risk of washing residue.As can be seen from Figure 8,the congealed capsules made of Jk1 #,JK2 # and GC3 # membranes whose compatibility results are completely dissolved within 450 s have no residue in the machine washing test;GC4#,there is a small amount of residue in the machine washing test within 450 ～ 600 s;The capsules made by the two domestic PVA film with compatibility results of more than 600 s still have more residues after 15 min machine washing test.At the same time,it is also necessary to pay attention to the film breaking time in compatibility.In consideration of safety,the film breaking time of coagulated capsules shall not be less than 30 s to avoid accidental eating ,all sample tested this time can meet the requirement.
Figure 7.Compatibility of PVA film from different manufacturers
Figure 8.Test results of 15-min machine washing performance of Laundry Gel made by different PVA film
Laundry capsules is still an emerging sub category for China’s clothing care market.If this category can develop healthily and well,the key is to grasp the product quality,which requires the joint efforts of water-soluble film manufacturers and daily chemical enterprises.
