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A Herbicide for Wet Weather

today:

tomorrow (without HW):

tomorrow (with HW):

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Herbicide for Wet Weather 2

activity

0 10 20 30 days

HW

HW-Hyper

the competition

HW

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Microcapsules

0 10 20 30 days

HW-Hyper

10-9

10-13

10-15

externalhumidity

D

m s

2 1

diffusioncoefficient

ingelatine

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4

1 herbicide forwet weather

2

capsule design

usingcapsules

delivering capsules

- release time

- coverage

- strength

making capsulesby coacervation

process steps6

process

design other

market

design

product

design

idea finding

defining theproduct

Development

35

- storage properties

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Defining the Product (1)

We really have Two Productscapsule in package before application

herbicide in the garden after application

form function needs

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Capsules before Application

carrier

safe usage

easily applicablestrong enough

capsules

form function needs

bring weed killer

into garden

specifications

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Herbicide after Application

form function needs

weed killer

kills no flowers

controlled release

dispersedcapsules

clean garden

specifications

kills weeds

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Design of the capsule

d

release time

application

coverage

strength

diameter

thickness

properties ?

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Release Pattern

0 rt t

m

zero order process

0contentrate

1 2

0 rt t

m

constant release rate

have the same characteristics

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Diffusivity versus

Humidity10-9

10-13

10-15

122

sm OHD

externalhumidity

0.0 2.0

volume fractionwater in polymer

diffusivity of active materialin gelatine copolymer not

available; expected to

show similar trends

herbicide activity dependson relative humidity

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Mass Transfer from a Capsule

c R R

cKcR

0c

herbicide

capsule

ccKDAdt

dMM thin capsule

0c

cKDdM

2

d

DdcK

dc

M

M

t 2

3

6

KD

dt 6

release time

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Release Time

kind of polymer

cross linking

size of HW molecule

1 KtrK

kind of polymer

cross linking

size of HW molecule1DtrD

humidity

rt to be chosen

dtr d to be chosen

depends on:

we can greatlyinfluence the

release time by ourdesign choices

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Kind of Delivery

HW

capsules

m10

capsulesm300

a spray can (household) can onlydeliver small (micro) capsules

a plane can only deliver large capsules;small ones blow away

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Coverage

mdiameter 2mparticles

take 1 kg (10-3 m3) ofcapsules per hectare (104 m2)

310

410

510

2102

5102

8102

mm3.0d

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product has to remain stable

product should not be released

product should not take up much

space

should be safe when taken out

Storage

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Coacervation

gummi arabicum gelatine

water at pH 4.5, 50 oC

charge

0

pH5.4

networks

these form a polymerrich phase

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Laboratory Recipe

filtering, washing, (drying)

3 g gummiarabicum

100 mLwater

3 g gelatine

12 mL HW(immiscible)

5.6pH

5.6pH

dispersing

mixing pH 4.5 cooling cross-linking55 oC 5 oC

pH 910 mL

formaldehyde

coacervation

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Flow sheeting

disperse

cross link

mix

pH